An international ten-centre double-blind trial comparing hCG with placebo in the management of habitual abortion was conducted. The dose regime for hCG used was 10,000 IU i.m. on first diagnosis of pregnancy, 5000 IU thence twice weekly to week 12, followed by once weekly up to week 16. Identical ampoulage of placebo was used. Seventy-five patients completed the trial. Thirty-six received hCG and thirty-nine placebo. 83% of the pregnancies on hCG were successful compared with 79% on placebo (P = 0.45). Of the 25 defined as having no cause for their habitual abortion history, 83% on hCG were successful, as were 85% on placebo (P = 0.73). No significant differences were found between the two therapies in terms of delivery weight, placental weight or neonatal Apgar score. This study fails to confirm previous promising placebo-controlled data advocating the use of hCG in habitual abortion.