Since retinoids affect collagen metabolism, nine females and two males with keloids were treated with 0.05% tretinoin topically for 12 weeks. The lesions had been present for an average of 7 years prior to therapy. Changes in size were evaluated by serial kodachromes, tape measurements, and appreciation of volume using dental moulages. Two patients abandoned the study due to irritant contact dermatitis. A significant decrease in weight (p less than 0.04) and size (p less than 0.01) was found when comparing the status of the lesions at the beginning of the study and at week 12.