Sedentary adults (N = 379) were randomly assigned in a 2 x 2 design to walk 30 min per day at a frequency of either 3-4 or 5-7 days per week, at an intensity of either 45%-55% or 65%-75% of maximum heart rate reserve. Analyses of exercise accumulated over 6 months showed greater amounts completed in the higher frequency (p = .0001) and moderate intensity (p = .021) conditions. Analyses of percentage of prescribed exercise completed showed greater adherence in the moderate intensity(p = .02) condition. Prescribing a higher frequency increased the accumulation of exercise without a decline in adherence, whereas prescribing a higher intensity decreased adherence and resulted in the completion of less exercise.