A study of the crura of the diaphragm and their innervation from the phrenic nerve was made in 22 fresh specimens and four embalmed specimens. The arrangement of the musculature was found to be essentially the same as that described by Low in 1907. The portions of the crural musculature passing to the right and left of the esophagus did not decussate anterior to the esophagus as these fibers insert into the central tendon. The right and left phrenic nerves divided into three to five divisions at the pericardiodiaphragmatic angle. Most commonly, these divisions are: anterior, posterior and lateral. If there are more than three divisions involved, there is usually a medial division present and/or a subdivision of one of the other divisions. It is the posterior division or its posteromedial branch which contributes to the innervation of the crura. None of the other divisions contributes to the innervation of the crura. Secondary branches of either the posterior division or the posteromedial branch do not cross to the contralateral side.