1. Menopausal controls not administered estrogen replacement therapy (ERT), or menopausal women taking 10 mg of tamoxifen bid had serum samples collected. 2. When controls were compared to treatment, significant elevations in the TRI (triglycerides), SGOT (serum glutamic oxalacetic transaminase), SGPT (serum glutamic pyruvic transaminase) and the GGT (gamma gluteryl transferase) were found in the tamoxifen group. Liver enzymes were elevated but still within the normal range for the tamoxifen-treated group. 3. The results from this study suggest that the use of tamoxifen citrate for adjuvant therapy in women with breast cancer causes no major alterations in the blood chemistry of menopausal women. The elevations observed were still within the normal ranges of menopausal women with the exception of the triglycerides.