Coronary arterial disease in the cardiac allograft has emerged as the most serious long term complication of cardiac transplantation. The influence of patient-related and other potential risk factors on the development of coronary arterial disease at 1 year subsequent to cardiac transplantation was examined in 207 recipients. The mean age of donors in patients with coronary arterial disease was 28.5 +/- 9.5 years, compared to 22.6 +/- 7.9 years in patients without coronary arterial disease (P less than 0.01). Eight of the 35 patients who received immunosuppression by means of prednisone and azathioprine developed coronary arterial disease compared to 5 of the 172 patients who were treated with cyclosporin and azathioprine without routine oral prednisone (P less than 0.01). The relationship of levels of serum lipids to the subsequent development of coronary arterial disease was investigated in 95 patients with angiographically normal coronary arteries one year after cardiac transplantation. The cumulative probability of coronary arterial disease in those with total cholesterol greater than 5.8 mmol/l was 9.3% at 2 years (n = 40), 24.4% at 4 years (n = 21) and 45% at 4 years (n = 9) compared with 4.3% at 2 years (n = 45), 7.4% at 3 years (n = 32) and 14% at 4 years (n = 14) in those with a total cholesterol less than 5.8 mmol/l (P less than 0.05). Similarly, the incidence of coronary arterial disease was increased in patients with serum triglyceride greater than 1.4 mmol/l (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)