Sixteen Roman Catholic parishes have been targeted in a citywide reorganization that could include mergers, the reassignment of priests and the closing of some landmark churches, pastors were told at a meeting yesterday.

The "restructuring," which covers parishes from West Baltimore to Highlandtown, includes the historic St. Michael the Archangel at Lombard and Wolfe streets. The church, established in 1852, is on the National Register of Historic Places, and its first pastor was John Neumann, a canonized saint.

Some large churches could be replaced by building smaller, more manageable churches, Auxiliary Bishop John H. Ricard said, commenting on a reorganization whose outline was first reported Saturday.

The restructuring plan will be decided by November and the "difficult decisions" will go into effect within a year, he said after conducting a five-hour, closed-door meeting with 125 clergy and staff from the 57 city parishes.

Shortages of priests, urban parishioners and money have triggered the reorganization, the bishop said.

Noting that once large and growing urban churches "are providing fewer baptisms and weddings, while welcoming fewer converts and performing more funerals," he said, "These are important trends, and we cannot maintain the status quo."

He said, "The church buildings and physical plants at many of these parishes are at once historic and beautiful, yet oversized and in urgent need of repairs and renovations."

At St. Michael, about $1 million was spent recently on restoration by the Redemptorist order that staffs the church, but about another $1 million is needed for a new roof, a parish leader said.

A proposal that has upset members of St. Michael's laity would close it and move the parishioners to St. Patrick on Broadway, where major reconstruction was completed recently -- with insurance money -- after a fire nearly destroyed the church in 1983.

The 16 troubled parishes that Bishop Ricard listed yesterday included six where pastors or lay leaders were recently advised about possible closings.

They are:

* St. Ann at Greenmount Avenue and 22nd Street, the home parish of the late Cardinal Lawrence Shehan, founded 1873.

* St. Stanislaus Kostka at 700 S. Ann St. in Fells Point, one of Baltimore's three traditionally Polish-speaking parishes, founded 1879.

* St. Cecilia at Windsor Avenue and Hilton Street, founded in 1902 and now ministering to a mostly black membership.

* Our Lady of Lourdes at Liberty Heights Avenue and Edgewood Road in Ashburton, also a center for black Catholics, founded in 1925.

* Holy Redeemer Chapel at 800 S. Oldham St., founded in 1944 as a mission of Sacred Heart of Jesus Parish in Highlandtown.

* St. Gerard Chapel at Charlotte and Cardiff avenues in O'Donnell Heights, also founded in 1944.

At the six, Bishop Ricard said, the attendance has fallen below 300 at all weekend Masses and there are compelling reasons -- including proximity to other underused churches -- to consider closing or merging them.

Publicly added yesterday to the endangered list, along with St. Michael and St. Patrick, were:

* St. Alphonsus at Park Avenue and Saratoga Street, founded by German-speaking Catholics in 1845 and a traditionally Lithuanian parish for many years. The Gothic Revival church, designed by noted architect Robert Carey Long Jr., is considered one of Baltimore's architectural treasures.

* St. Mary, Star of the Sea, at 1419 Riverside Ave., founded in 1868, and Holy Cross, established 10 years earlier at 108 E. West St. These two South Baltimore parishes were recently "twinned" in an arrangement that places a pastoral team of one priest and two nuns in charge of both. Last week, Bishop Ricard called this a model solution for other city churches that are strapped financially.

* Immaculate Conception at Mosher Street and Druid Hill Avenue, founded in 1850 and staffed by the Vincentian Fathers.

* St. Martin at Fulton Avenue and Fayette Street, established in 1865.

* St. Peter the Apostle at Poppleton and Hollins streets, established in 1842.

* Most Precious Blood at 5010 Bowleys Lane, established in 1948. It is the newest parish on the list.

* St. Wenceslaus, a historically Bohemian parish at Collington and Ashland avenues, established in 1872. St. Katherine of Siena Parish on Luzerne Avenue, founded in 1902 and closed by the archdiocese in 1986, was merged at that time with St. Wenceslaus.

St. Katherine and the Church of St. James and St. John, which also was the result of a parish merger, were both closed in 1986 -- the last time that the archdiocese took such a step to address the membership decline in Baltimore.

"There is a set of realities here that we simply must address," Bishop Ricard said after the meeting, held at St. Jerome Church at Scott and Hamburg streets. "At one time, our family of 57 Catholic churches in Baltimore served a young and growing population of more than 150,000 parishioners.

"In sheer demographic terms, that same number of churches is serving an older population of fewer than 33,000 parishioners, who do not have the financial resources that young, growing families have."

The flight of more prosperous Catholics from Baltimore to surrounding counties already had created fiscal problems for many of the urban churches when Bishop Ricard was appointed in 1984 under Archbishop William D. Borders, now retired.

One of Bishop Ricard's first important duties as urban vicar, the auxiliary bishop in charge of the city sector of the sprawling Baltimore archdiocese, was to preside over the closing of St. James and St. John and of St. Katherine amid much controversy and bitterness.

As they left yesterday's meeting, some pastors and parish leaders appeared glum. Others appeared relieved that their churches were not on the endangered list.

Charles G. Tildon Jr., former president of Baltimore City Community College and a lay leader of St. Gregory the Great Parish, said the archdiocese has no other choice than to make the hard decisions outlined by Bishop Ricard if it wants to remain viable in Baltimore.

But at St. Michael, former Parish Council president and long-time lay leader Pasquale Spinnato said he had resigned from the council because of what he considered a lack of candor by archdiocesan officials during discussions the past year. "We feel we have been used," he said.