In order to examine whether the duration of the follicular phase and changes in daily gonadotrophin dosages impact IVF outcome, a retrospective analysis of women who underwent oocyte retrieval and fresh embryo transfer was performed. Among the parameters assessed were the number of days of gonadotrophin stimulation, changes in the daily dosage of gonadotrophins, total ampoules of gonadotrophins, embryo implantation rates, clinical pregnancy rates and ongoing pregnancy rates. The number of days of gonadotrophin stimulation, as determined by standard follicular size criteria did not appear to influence IVF outcomes. There was no significant difference in pregnancy rates between women who were stimulated for <9 days, 10-11 days or >12 days. When grouped by amount of starting daily dose of gonadotrophins there was a significant inverse relationship between gonadotrophin requirements and pregnancy rates (P=0.02). The data suggest that the success of an IVF cycle depends on the ovaries' ability to develop follicles of the appropriate size, not the speed at which the ovaries perform this function.