The internal thoracic artery was studied because of its recent use in the revascularization of the myocardium in patients with coronary artery disease. The artery of 50 cadavers of adult individuals of either sex, whose age ranged from 20 to 84 years, was studied after neoprene latex injection. Its origin, relation to the phrenic nerve and origin of the pericardiacophrenic artery were investigated. The left and right phrenic nerves cross the artery anteriorly in 54% of the cases and posteriorly in 14%. The right nerve crosses the artery anteriorly and the left posteriorly in 22%, and the reverse occurs in 10%. The origin of the internal thoracic artery is much more frequent from the subclavian artery (80%) than from a common trunk with other arteries (20%). The pericardiacophrenic artery is a branch of the internal thoracic artery in 99% of the cases and the average distance between the origins of these two arteries is 3.9 +/- 1.3 cm.