The topical tretinoin epoch began almost 30 years ago in the laboratories of Stüttgen where he first recognized that a vitamin A derivative, tretinoin, had the potential to be a truly significant form of dermatological therapy. His early clinical trials in a variety of skin disorders provided the first indication of topical activity for the retinoids. Kligman evaluated further the utility of topical tretinoin; focusing his attention on acne. Through these initial studies, topical tretinoin became a fundamental treatment modality for acne. Soon after topical tretinoin was made available, elderly patients using it to treat acne noted a general improvement in the quality of their skin. Kligman began open clinical trials to investigate the effects of topical tretinoin on treatment of photodamaged skin. Positive findings from these trials led to double-blind, vehicle-controlled pilot studies which supported the concept that topical tretinoin could improve the fine wrinkling, mottled hyperpigmentation and tactile roughness which are characteristic of photodamaged skin. These results were verified in two large double-blind, multicentre studies of approximately 700 patients that used not only clinical and patient evaluations but also biopsies and skin surface replicas.