Tamoxifen has been found to be safe and effective in gynecological cancer patients with normal renal function. However, to our knowledge, no data exist regarding its effectiveness and toxicity in gynecological cancer patients with chronic kidney disease (CKD). Therefore, we retrospectively evaluated the effects of tamoxifen in patients with recurrent gynecological cancer and CKD. We collected clinical and demographic data for all patients. CKD was defined as a creatinine clearance (CrCl) level of less than 90 mL/min/1.73 m(2), in accordance with the National Kidney Foundation Kidney and Dialysis Outcomes Quality Initiative, and further categorized as mild, moderate, or severe (CrCl levels of 60-89, 30-59, and <30 mL/min/1.73 m(2), respectively). Twenty-nine patients were included in the study--22 with epithelial ovarian cancer, 4 with peritoneal cancer, and 3 with fallopian tube cancer. Thirteen patients had mild CKD, 13 had moderate, and 3 had severe. Most patients had been treated with 20 mg/day of tamoxifen every 4 weeks. The median duration of treatment was 5 months (range, 1-52 months). The overall complete response, partial response, stable disease, and disease progression rates were 0%, 10%, 41%, and 48%, respectively. Twenty-one percent of patients experienced hot flashes, and 7% experienced nausea. No major adverse reactions occurred. These findings were similar to those for gynecological cancer patients with normal renal function. In conclusion, 20 mg/day of tamoxifen is safe and effective in gynecological cancer patients with CKD.