The preperitoneal fascia of the groin is distinct from the transversalis fascia, although often mistaken for it. This distinction, and other special features of this fascia in the inguen, are more readily appreciated in the course of the preperitoneal approach than by the conventional transinguinal approach. Certain features of this fascia which are of practical surgical significance are emphasized, especially those concerning operations for hernias, hydroceles, or undescended testes in infancy and childhood. These special features include the preperitoneal fascial ring or secondary internal ring, which appears to have been confused in the past with the transversalis fascial opening or internal ring proper. Other features concerning the relative merits of the preperitoneal approach to groin hernias as opposed to the conventional transinguinal approach are discussed.