The adductor hallucis muscle (ADH) is evolutionally and functionally important, but no detailed morphological data about this muscle in the human body is available. In the present study, we examined the origin and insertion of the oblique and transverse heads of the ADH. Forty-five feet (20 right, 25 left) of 34 cadavers (13 men, 21 women, average age of 80 years old) were used in the present study. The origin, insertion and nerve supplies of the oblique and transverse heads of the ADH were macroscopically examined in detail. Most commonly, the oblique head of the ADH arose from the bases of the 2nd, 3rd and 4th metatarsal bones, the plantar metatarsal ligaments spanned between the bases of the 2nd, 3rd and 4th metatarsal bones, the lateral cuneiform bone, the fibrous sheath of the tendon of the peroneus longus muscle and the long plantar ligament, and inserted into the lateral sesamoid bone of the great toe and the capsule of the 1st metatarsophalangeal joint. Most commonly, the transverse head of the ADH originated from the capsules of the 3rd and 4th (and occasionally 5th) metatarsophalangeal joint and the deep transverse metatarsal ligaments, and inserted into the lateral sesamoid bone of the great toe, the capsule of the 1st metatarsophalangeal joint and lateral surface of the base of the 1st proximal phalanx. This muscle was classified into four types based on the origin of its oblique head and was classified into three types based on the origin of its transverse head. The percent ratio of the weight of the oblique head to the total weight of all the intrinsic muscles of the foot was 9.4% +/- 1.5, and the transverse head was 1.5% +/- 0.6 (n = 14). The transverse head of ADH tends to be reduced in size in the human, but the oblique head is well developed with no sign of reduction.