232 Veterans were randomized to either the physical activity intervention group or the attention control group. Participants randomized to the physical activity intervention group participated in an individualized physical activity counseling session at baseline, conducted by an exercise physiologist, with guided goal setting to increase physical activity gradually to at least 150 minutes/week of moderate intensity. An additional 14 intervention counseling contacts, generated by participants' responses to physical activity questionnaires and individually tailored computer-generated expert system feedback messages based on stages of the motivational readiness for change model, were conducted via postal mail over the subsequent 12 months in parallel with routine primary care. Newsletters providing additional support and suggestions for increasing physical activity were also part of the mailed counseling contacts. Participants randomized to the attention control group participated in a generalized healthy lifestyle counseling session at baseline, conducted by a health educator, which included limited advice to become more physically active. Fourteen follow-up wellness newsletters that focused on healthy lifestyle issues other than physical activity were sent to participants via postal mail over the subsequent 12 months with the same frequency of contact as for the physical activity intervention group and in parallel with routine primary care. Assessment of effectiveness occurred at baseline, 6, and 12 months.