Physical inactivity is associated with higher mortality rates in most studies in men, but studies in women are more equivocal. The purpose of this study was to evaluate the relationship of sedentary living habits to all-cause mortality in women. A group of 3,120 adult women completed a preventive medical examination, and were followed for approximately 8 years for mortality. There were 43 deaths and a total of 25,433 person-years observed during follow-up. Physical fitness was assessed at baseline by a maximal exercise test on a treadmill, and physical activity was estimated by a self-administered questionnaire. Age-adjusted all-cause mortality rates were significantly inversely associated with physical fitness. Death rates were 40, 16, and 7 per 10,000 person-years of follow-up across low, moderate, and high categories of physical fitness, respectively. However, death rates did not differ across low, moderate, and high categories of physical activity. These findings are different than for men in the same study, where both physical activity and physical fitness were inversely associated with mortality risk. We attribute the lack of association between physical activity and mortality in women to be due to inadequate assessment of activity, and that this also is the likely explanation for the difference in results between women and men in published studies of physical activity and mortality.