OBJECTIVE: To evaluate the efficacy of a homeopathic treatment of plantar warts. DESIGN: Randomized double-blind placebo-controlled trial. SETTING: Hospital-based family medicine unit. PATIENTS: Patients were recruited from the unit, through advertisements in the local media and through personal contacts with colleagues. Of the 853 people screened between December 1987 and January 1989, 174 met the eligibility criteria (age 6 to 59 years and presence of one or more plantar warts untreated during the previous 3 months) and agreed to participate; 162 (93%) completed the 18-week follow-up. INTERVENTIONS: The 6-week homeopathic treatment consisted of thuya 30 "centésimal hahnemannien" (CH) (one tube containing 200 pellets weekly), antimonium crudum 7 CH (5 pellets daily) and nitricum acidum 7 CH (one tube containing 200 pellets daily). The placebo pellets were identical to the treatment pellets in appearance and taste. MAIN OUTCOME MEASURE: The proportion of healed patients; a patient was considered healed if all of the warts had disappeared. MAIN RESULTS: The rates of healing at 6, 12 and 18 weeks were 4.8%, 13.4% and 20.0% respectively in the homeopathic treatment group and 4.6%, 13.1% and 24.4% in the placebo treatment group. CONCLUSION: The homeopathic treatment was no more effective than the placebo treatment of plantar warts.