The purpose of this study is to demonstrate the use of a self-report exercise log and a heart-rate monitor in the measurement of adherence to the dimensions of an exercise prescription and to propose an alternative way to define adherence to a 24-week home-based women's walking program, which reflects the dynamic process of behavior change. Adherence was measured with exercise logs, Polar Vantage XL Heart-Rate Monitors, and pre- to postintervention change in VO2 max. Of the dimensions of the exercise prescription, frequency of walks documented by both the heart-rate monitor and the exercise log had a higher correlation than duration and intensity of walking, with change in VO2 max suggesting that frequency was potentially the most predictive adherence measure. Examination of the total number of walks and the number and sequence of weeks without walks over the 24-week intervention revealed dynamic patterns of adherence suggesting variation in the degree of behavioral change.