SummaryThe studies were performed using stereomicroscopic dissection, and light microscopy examination on hearts of healthy and fertile non-human primates (Macaca fascicularis) of both sexes. The results indicate that the anatomy of the coronary arteries offers points of similarity as well as departure from humans. The blood supply to the hearts was by left [LCAI and right (RCA) coronary arteries. The LCA averaged 1.78 ± 0.29 (SDlmm (range 1.40-2.40 mm) in external diameter at its origin, and 4.34 ± 1.29 (SD)mm (range 1.8-6.5 mm) in length. It usually terminated by dividing into a left anterior descending artery (LAD)and the circumflex branch [CXA).The CXA branch coursed along the left part of the atrioventricular groove and gave off a varying number of branches to the left ventricle and atrium along its course. It averaged 1.14±0.30 (SD)mm (range 0.70-1.70mm) in external diameter at its origin. The LAD averaged 1.28± 0.25 (SD)mm (range 0.90 ± 1.80mm) in external diameter at its origin. In 73% cases the LAD continued over the apex to course dorsally in the posterior interventricular groove, and gave off a varying number of diagonal and septal branches. The RCA arose from the right aortic sinus and coursed along the right part of the atrioventricular groove and averaged 0.94±0.15 (SDlmm (range 0.70-1.20mml in external diameter at its origin. The posterior descending coronary artery (PDCA) arose from the LCA in 55% of the cases, and from the RCA in 45%. Myocardial bridges (MB)were present in 54% of the hearts and over the LCA branches exclusively. The average length of all MB was 5.68 ±3.31(SD) mm (range 2.4-11.5 mm). The coronary arteries of Macaca fascicularis are medium sized muscular arteries with well developed tunics intima, media and adventitia, and so resemble human arteries more closely than the dog. Therefore, we suggest this primate species might be a useful model for physiological studies on the coronary circulation.