Objective: To study the beneficial effects of 12 weeks exercise at home, which is a part of cardiac rehabilitation program, on physical fitness and quality of life and to study drug usage and factors that might impede regular exercise during 1-year follow up period in post-acute MI patients. Patients and method: This was a quasi experimental study performed on a single group of 18 subacute MI patients whose acute stage was treated as inpatients in Prapokklao Hospital, between Jan.- Dec. 2001. Among the 18 cases, there were 17 males and 1 female, with the age ranging from 37 to 79 years.  When discharged from the hospital, and appointment was made for each patient to come to the hospital special cardioclinic once weekly for 12 consecutive weeks, where they were provided with health education and exercise-skill training program for cardiac rehabilitation in the form of group activity, in order to set up appropriate exercise behaviour for them.  The results were collected both before and after 3 months of study.  Data concerning physical fitness, body weight, blood pressure and : at rest and at 6 minutes after walking and distance were recorded.  Fatigue level during 6 minutes walking exercise was recorded as well, using Borg rating scales. All of patients were asked to fill the SF-36 questionnaire forms in order to assess quality of life.  Their drug usage and factors impeding their regular exercise during 1-year follow-up period were also recorded and analysed. Results: Kolomogorov-smirnor statistics was used to test for normal distribution of data.  The data collected before and after 12-week-exercise program were compared, using paired t-test and Sign test.  There were no significant changes in BW (64.86 kg VS 64.94 kg, p > .05) and decrease of BP at rest (133.89/ 84.11 mmHg VS 131.67/ 81.11 mmHg, p>.05), whereas there were statistically significant decrease of BP after 6 minutes walking (142.78/ 84.44 mmHg VS 137.78/ 81.88 mmHg, p<.05), pulses at rest (78.88/ min VS 69.78/ min, p<.05), pulses after 6 minutes walking (122.00/ min VS 107.67/ min, p<.05) and Borg rating scale of fatigue level (13.65 VS 12.11).  The 6-minute-walking distance increase significantly (532.18 meters VS 583.41 meters, p<.05) and there was an improvement of quality of life (44.47 percent VS 69.12 percent). During 1-year period of follow-up, 77.8 percent of the patients had regular exercise and 61.11 percent discontinued using cardiovascular drugs treating their illness.Conclusion: This study showed that health education by group activity in addition with exercise-skill training program could help patients in subacute stage MI to exercise properly, leading to improvement of their physical fitness, quality of life and prognosis. However this study could not point out that the improvement was solely contributed to by exercise.  There could be some other factors, such as better food-consumption bahaviour and tension-relieving activities, contributing to the improvement.  This study helped rehabilitation team to realized the importance of giving the health education and training program to future case of subscute MI in order that they can exercise properly and consistently.