Serum biochemical profiles were compared in matched groups of premenopausal and postmenopausal women. Significantly higher concentrations of sodium, urea, calcium, albumin and alkaline phosphatase were found in the postmenopausal group. In the postmenopausal group, following treatment with sequential mestranol and norethisterone, significant reductions were recorded in the concentrations of sodium, urea, calcium, albumin, alkaline phosphatase and glucose and significant increases were recorded in the concentration of globulin and in body weight. The findings suggest that haemoconcentration may take place after the menopause and that this effect may be modified by hormone treatment. No adverse effect on liver function was noted following the hormone treatment.