The birthday card Mary Goodman has mailed to her best friend for the past 20 years is on its way to Venice, Fla., in time for Donna Knauer's birthday today.

Mary usually mails it from her home in Crownsville the first week of June because she thinks Donna was born on the 15th or 16th, and she's known her too long now to ask. Donna says it's the 18th - and Mary should know better - but the date is not important. What matters to them both is not the "Happy Birthday" embossed on the outside, but everything written inside, over the years.

Inside are 41 pages of note paper stapled together. They chronicle two decades, 41 birthdays, seven marriages, the growth of eight children, the birth of six grandchildren, several moves, many jobs. The bond that ties them together is the rare kind of friendship that for some lucky people can last a lifetime.

Dear Friend,

Times are hard, so I am conserving by recycling this card.

That was how the tradition started. Donna wrote those words in the card Mary had given her two months earlier. This was Aug. 18, 1982, when the card decorated with two kittens and a straw wagon cost 90 cents at a Rexall Drug Store where they lived in Lexington Park.

By the time the ball landed back in Mary's court, she had moved to Texas. She was still there a year later when, cleaning out closets, she came across the card.

Donna,

Times are still hard but memories of friendship and happiness hold fast. So I recycle this card with love.

It went that way the first years, as a joke, and it wasn't until later that the card took on meaning and weight. At first, the two women wrote the names of the men in their lives behind an ampersand, alongside theirs. Then Mary moved back to Maryland, Donna moved to Florida, and the names of the men changed.

I guess time will always be hard, but this card seems to go on and on, just as you and I do.

Another year, another beginning ...

They found themselves far from the place where their friendship began, in 1970, when Donna's dog broke free of its chain and knocked over Mary's 5-year-old son. Mary was 26, Donna 27. Although Mary was the kind of person who never spoke her mind and Donna was just the opposite, a knot was tied between them and it hasn't loosened or frayed since.

Their friendship has lasted through good times and bad.

This card has seen me in two states and through two marriages and one divorce, several deaths and Lord knows what else. But we endure. This is our card's 10th anniversary. Let's hope for 10 more.

It has endured problems big and small.

I'm 50, I'm fat and unemployed. So what do I do? ... Miss you and could really use a friend.

Over time, their differences mattered less, and the things they shared mattered more: being near the water, eating at outdoor cafes, shopping at consignment stores, Willie Nelson, the Redskins.

Some years, they wrote each other long letters. Others, they telephoned once or twice. Most years, their only connection was the card, and maybe this is why they have held it so tight.

This year has brought about even more changes for both of us as we continue to soul search ... My wish for you this year will be that you, too, will become happy and hopeful and that it will last forever just as our friendship has done.

Mary's handwriting was always harder to read than Donna's. Donna sometimes wrote her notes on stationery from wherever she worked. Mary started typing hers on a computer in recent years, and all the while, their lives continued to change.

Mary was diagnosed with emphysema, Donna with diabetes. Mary recently has chosen to stay single, Donna has remarried. Mary has started a job at a florist. Donna has become a paralegal.

Another year gone. Do you believe it? How old are we going to get? Or rather, how old is this card going to get?

In time, Mary and Donna have come to see themselves and the card through wiser eyes. They shake their heads at the things that used to upset them.

My thought for you this year is "Count Your Blessings." For all we've been, and all that we will be, we're two cats that have landed on our feet.

One of my blessings is our friendship.

Donna underwent a quadruple bypass a few years ago, and Mary went to Florida to see her. During recovery, Mary thought Donna would like a new birthday card, for the "new" her. Donna said forget it; she wanted the old.

So even though it was past June, Mary sent the old card and inside, she wrote:

Please take care of yourself and do the right stuff. I need for you to be there for me. Just as I'll be there for you.

The card is on its way to Venice now, and as soon as it arrives, Donna will take it to her bedroom, close the door, make herself comfortable, and only then, open and read. From start to finish, she will savor every page. She will have the card less than two months before she has to send it back to Crownsville.

Meanwhile, Mary will wait until the middle of August before she starts watching the mail, same as always, to see what her friend has to say.