Background: Recent meta-analyses of randomized controlled trials in homeopathy have suggested that homeopathy is more than a placebo response.Objective: Comparison of the effectiveness of homeopathy in primary care with conventional medicine in primary care for three commonly encountered clinical conditions.Design: An international multicenter, prospective, observational study in a real world medical setting comparing the effectiveness of homeopathy with conventional medicine.Participants: Thirty (30) investigators with conventional medical licenses at six clinical sites in four countries enrolled 500 consecutive patients with at least one of the following three complaints: (1) upper respiratory tract complaints including allergies; (2) lower respiratory tract complaints including allergies; or (3) ear complaints.Main Outcome Measures: The primary outcomes criterion was the response to treatment, defined as cured or major improvement after 14 days of treatment. Secondary outcomes criteria were: (1) rate of recovery; (2) occurrence of adverse events; (3) patient satisfaction; and (4) length of consultation.Results: Four hundred and fifty-six (456) patient visits were compared: 281 received homeopathy, 175 received conventional medicine. The response to treatment as measured by the primary outcomes criterion for patients receiving homeopathy was 82.6%, for conventional medicine it was 68%. Improvement in less than 1 day and in 1 to 3 days was noted in 67.3% of the group receiving homeopathy and in 56.6% of those receiving conventional medicine. The adverse events for those treated with conventional medicine was 22.3% versus 7.8% for those treated with homeopathy. Seventy-nine percent (79.0%) of patients treated with homeopathy were very satisfied and 65.1% of patients treated with conventional medicine were very satisfied. In both treatment groups 60% of cases had consultations lasting between 5 and 15 minutes.Conclusions: Homeopathy appeared to be at least as effective as conventional medical care in the treatment of patients with the three conditions studied.