F patients (33 men, 10 women) with.a median age of 33 years (range 15-59) received double-blind medication consisting of bottles containing 100 ml of a 2% ketoconazole scalp gel or an identical placebo jgel on a computer-randomized basis. At entry into the study, the patients had had dandruff for periods ranging from 1 month to 25 years (median 4 years). Overall, the ketoconazole and placebo groups were not statistically different for sex, age, duration of dandruff, and previous therapy. Patients were instructed to wash their hair twice weekly for 4 consecutive weeks. The washing procedure had to be performed with plenty of warm water. The scalp gel was distributed over the scalp area by gently massaging and was left on the scalp for 3-5 minutes. Afterward, the hair was rinsed with plenty of warm water, and hair was dried with a warm air current. At the end of the 4-week treatment period, a final assessment of the objective symptom (desquamation) and subjective symptom (pruritus) was given. Also, the onset of improvement was recorded.