To obtain prognostic data on the likelihood of pregnancy in infertile women with no observable abnormalities at diagnostic laparoscopy, the occurrence of pregnancy was studied in a series of 229 patients. The cumulative conception rate during a follow-up period of at most 5 yr was 50%. The probability of pregnancy proved to decline with age and duration of infertility. The cumulative conception rate during the first year after laparoscopy was approx. 30%, and there was no significant difference between the patients that were treated with respect to other sub-optimal fertility factors (subfertile group) and the patients in whom no rational treatment could be instituted (unexplained infertility group). Implications of these findings with respect to the treatment of long-term infertility are discussed. Knowledge of pregnancy rates after infertility laparoscopy seems important for the evaluation of results of therapy in unexplained infertility.