All results on 106 women with failure of ovulation who were treated here with gonadotrophins up to November 1968 are summarised. Twenty-three patients failed to ovulate as judged by their excretion of pregnanediol, 39 appeared to ovulate without conceiving and 44 patients conceived and had 56 pregnancies. The dosage of FSH required to induce ovulation varied between 500 and 16,150 IU per monthly course. Adverse results of therapy were nine mild and two severe cases of hyperstimulation syndrome in 203 months with positive pregnanediol responses and there were five pregnancies with triplets or more. An additional case of triplets is included in the appendix. These complications did not appear to be associated with high dosages of FSH or HCG but were associated with elevated excretions of oestriol at the time of giving the ovulating dose of HCG and at the mid-cycle peak and of pregnanediol 8 days after the ovulating dose of HCG. Treatment with FSH which contained little LH was associated with fewer pregnancies with triplets or more but with more abortions than were those with FSH rich in LH. The importance of these results in modifying the method of treatment with gonadotrophins is discussed.