Background: Adherence is essential to a positive treatment outcome. Whether adequate doses of topically applied drugs are used among patients with dermatologic conditions has not been investigated adequately. Objectives: The objective of this prospective study was to determine to what extent first-time outpatients with dermatologic conditions apply the appropriate dosage of initial treatment with topically administered medication. Methods: Consultations with first-time patients in the dermatologic outpatient clinic were observed. Patients receiving a prescription for a previously untried topically administered drug were eligible. The expected quantity of topical treatment to be used by each patient was calculated from the affected skin area to be treated. The affected area was estimated in numbers of palms of the hand, and an amount of 0.25 g of ointment or cream was chosen as sufficient treatment to cover the area of one palm. Two weeks after the consultation, a questionnaire with items regarding the size of the affected area, intentions to follow the treatment, and the applied dose the previous day was mailed to each patient. The questionnaires were personally collected from the patients' homes and at the same visit the patients' topical drug containers were weighed on a balance. Both patients and staff were blinded to the particular study purpose concerning adherence and dosing. Results: In all, 17 patients were eligible. The majority received a prescription for topical corticosteroids, and the median area to be treated was 3 palms of the hand (interquartile range: 1.5-8). Two patients did not redeem their prescriptions. Only one patient used the expected dosage; in general median 35% (interquartile range: 22%-50%) of the expected individual dosages were used. Limitations: Only first-time patients who received a new and previously untried topical treatment were included, resulting in a small study size. Conclusions: Most first-time patients with dermatologic conditions underdose new topical treatments. Consequently, clinicians should always consider nonadherence when topical therapies fail.