OBJECTIVES: To investigate the efficacy of hCG in the management of recurrent early pregnancy loss. DESIGN: A prospective, randomized, controlled trial. SETTING: Miscarriage Clinic, Women's Hospital, Liverpool, United Kingdom. SUBJECTS: Eighty-one women attending the miscarriage clinic with idiopathic recurrent pregnancy loss were randomized to receive hCG supplementation or placebo in early pregnancy. MAIN OUTCOME MEASURE: The success rate or live birth rate. RESULTS: In women with regular menstrual cycles it was found that hCG had no beneficial effect, the pregnancy success rate being 86% in both groups. However, women with oligomenorrhea had a pregnancy success rate of 40% in the placebo group but a statistically significant improvement to 86% if hCG was given. CONCLUSIONS: Human chorionic gonadotropin can be recommended for idiopathic recurrent pregnancy loss in women with oligomenorrhea.