Frederick J. Rogers, 47, has been booked on suspicion of attempted sexual assault, burglary, lewd contact and indecent exposure.
Police say Rogers followed the woman for several blocks in a metallic blue Lexus sport utility vehicle.
The woman pulled into the drug store parking lot, and Rogers allegedly parked right next to her and started touching himself inappropriately.
The woman ran into the store and Rogers followed her, police say.
The woman eventually lost sight of him.
She left the store and notified police.
Surveillance cameras caught the suspect wandering around the store, apparently looking for the woman.
Anyone with information is asked to call El Segundo police at (310) 524-2216.