A published case report and anecdotal experience suggested that topical imiquimod is an effective treatment for stage 0 melanoma (lentigo maligna). To gauge the efficacy of this therapy, we undertook a trial of topical imiquimod in 30 subjects with histologically confirmed lentigo maligna. Thirty subjects with lentigo maligna were recruited for an open-labelled efficacy trial with daily topical application of imiquimod 5% cream for 3 months. Study subjects were enrolled from the Dermatology service of the University of Oklahoma, the Oklahoma City Veteran's Administration Hospital Dermatology service and from referrals for the study from other practitioners. In order to determine an initial response rate, a four-quadrant biopsy was carried out on all patients 1 month after cessation of treatment, targeting the most clinically and dermatoscopically suspicious areas. Of 28 evaluable subjects who have completed the 3-month treatment phase, 26 (93%) were complete responders and two were treatment failures at the time of the 4-quadrant biopsy. Over 80% of the 28 subjects that completed treatment have been followed for more than 1 year with no relapses. The results of this study demonstrate that topical imiquimod produces a high complete response rate in lentigo maligna when applied daily for 3 months.