Patients undergoing IVF, with or without intracytoplasmic sperm injection, were treated with either recombinant human FSH or urine-derived FSH. Response to ovarian stimulation was monitored by ultrasound examinations and measurement of serum oestradiol concentrations. To define any differences in embryo quality and hence assisted reproductive technology success rates, a retrospective analysis of 811 recombinant FSH versus 555 urinary FSH cycles was undertaken. Embryo quality was assessed as embryo cell number and degree of fragmentation. Implantation and ongoing pregnancy rates were also compared. Use of recombinant FSH resulted in a higher percentage of mature oocytes, improved embryo cleavage, with more embryos available for freezing and higher implantation rates compared with urinary FSH. Oocyte and embryo quality were superior when recombinant FSH was used for ovarian stimulation compared with urinary FSH.