The aim of this study was to analyse the changes in follicle stimulating hormone (FSH), luteinizing hormone (LH) and prolactin concentrations in the 3 months following oophorectomy in pre-menopausal women operated on for benign gynaecological conditions. Included in this analysis were 21 women (mean age 47 years, range 46-52) who underwent bilateral oophorectomy plus hysterectomy for fibroids or ovarian cysts. Plasma concentrations of FSH, LH and prolactin were measured before and on days 2, 4, 6, 14 and 30 after surgery; in 10 cases measurements were made on day 60, and in five cases on day 90 after surgery. Hormone concentrations were measured in duplicate daily samples, and immunoenzymatic assay kits were used for all the immunoassays. The FSH and LH concentrations increased constantly after surgery. Mean prolactin concentrations also increased from 12.1 ng/ml before surgery to 31.5 ng/ml on day 14 after bilateral oophorectomy, but decreased thereafter to 18.2 ng/ml on day 30, 10.9 ng/ml on day 60 and 6 ng/ml on day 90. In conclusion, transient (2-3 weeks) increased prolactin concentrations are observed after surgical castration.