In a series of 500 adult human embalmed cadavers the accessory obturator nerve has been looked for, bilaterally, and its formation and distribution studied. This nerve was formed by roots from the anterior primary divisions of L3 and L4 (63.6%) or L2, L3 and L4 (10.6%), or L2 and L3 (7.6%), or L3 (6.1%) or from the trunk of the obturator nerve (12.1%). The frequency of this nerve was found to be 13.2 percent (13.3 % in males and 12.9% in females) of the 1,000 specimens examined, with a predominance on the left side of the body (15.2 : 11.2). Some questions with regard to the variability of the frequency of this nerve referred to in the literature are analyzed and discussed.