Similarities in the phenotype observed in women with FSH receptor mutation and in FSH receptor knockout mice have clearly established a critical role of this protein in normal gonadal function. Two common single nucleotide polymorphisms in the exonic region of the FSH receptor gene have been shown to be associated with altered ovarian response in subjects undergoing gonadotrophin treatment. Recent in-vitro studies have shown that the A allele at the -29 position in the 5 untranslated region of the FSH receptor gene is associated with impaired transcriptional activity. Differential expression of the FSH receptor and its function may be one of the factors responsible for altered ovarian response. These observations prompted a study of the association between FSH receptor genotype at the -29 position and ovarian response in women undergoing gonadotrophin treatment. Analysis of the data revealed that the subjects with AA genotype at the -29 position required the highest amount of exogenous FSH for ovulation induction, and oestradiol concentrations before the day of human chorionic gonadotrophin administration were significantly lower (P = 0.015) compared with the GA genotype. The number of pre-ovulatory follicles and retrieved oocytes were lowest in the subjects with AA genotype. These results indicate that the AA genotype at position -29 may be associated with the poor ovarian response.