The focus of this study was the relationship of grip strength to age, physical activity and anthropometric factors, in a population of 255 post-menopausal women not on estrogen therapy (mean age = 57.6) and 55 women currently on estrogen replacement therapy (mean age = 56.9). Grip strength was measured as an indicator of muscular strength in the upper limbs. The grip strength of the estrogen users was significantly higher than that of the estrogen abstainers. Grip strength was related to age (r = -0.25, p less than 0.01), and the body habitus parameters of height (r = 0.36, p less than 0.01) and weight (r = 0.18, p less than 0.01). Although estrogen use was univariately correlated with strength (r = 0.16, p less than 0.05), multiple regression analyses revealed that only the height, age and physical activity were independent determinants of grip strength. These data suggest: height is the major determinant of upper body strength in older women; the reduction in physical activity with advancing age may contribute to strength decline, and modest increase in physical activity may retard the loss of strength that accompanies aging; the loss of ovarian estrogen in menopause may be related to the loss of strength in postmenopausal women.