Alternative therapies in general, and homeopathy in particular, lack clear scientific evaluation of efficacy. Controlled clinical trials are urgently needed, especially for conditions that are not helped by conventional methods. The objective of this work was to assess the efficacy of homeopathic treatment in relieving symptoms associated with premenstrual syndrome (PMS). It was a randomised controlled double-blind clinical trial. Two months baseline assessment with post-intervention follow-up for 3 months was conducted at Hadassah Hospital outpatient gynaecology clinic in Jerusalem in Israel 1992-1994. The subjects were 20 women, aged 20-48, suffering from PMS. Homeopathic intervention was chosen individually for each patient, according to a model of symptom clusters. Recruited volunteers with PMS were treated randomly with one oral dose of a homeopathic medication or placebo. The main outcome measure was scores of a daily menstrual distress questionnaire (MDQ) before and after treatment. Psychological tests for suggestibility were used to examine the possible effects of suggestion. Mean MDQ scores fell from 0.44 to 0.13 (P<0.05) with active treatment, and from 0.38 to 0.34 with placebo (NS). (Between group P=0.057). Improvement >30% was observed in 90% of patients receiving active treatment and 37.5% receiving placebo (P=0.048). Homeopathic treatment was found to be effective in alleviating the symptoms of PMS in comparison to placebo. The use of symptom clusters in this trial may offer a novel approach that will facilitate clinical trials in homeopathy. Further research is in progress.