Despite potential for major benefits, middle-aged women have low levels of aerobic exercise. A 12-week minimal-intervention exercise program was evaluated with female university employees aged 40 to 61. Following pre-testing, participants were randomly assigned to exercise or wait-list control. Testing was repeated at 12, 24 and 48 weeks. Exercisers improved significantly in aerobic fitness at 12 and 24 weeks, both groups decreased resting arterial pnssurc and body composition measures, and improved in exercise knowledge. Effects, however, were not well maintained at 48 weeks. These results are comparable to those obtained fmm intensive interventions and, while modest, suggest that a threshold has been reached for the modification of physiological control systems which are important for reducing cardiovascular disease risk. Middle-aged women face major social and practical baniers to regular exercise, and the minimal-intervention approach allows for a combination of flexibility and structure which seems appropriate for this group.