Introduction: Incomplete obliteration of processus vaginalis (PV) has been suggested to result from the persistence of smooth muscle, which should normally disappear after taking part in the descent of testis. Since apoptosis is the mechanism of disappearance, the presence or absence of apoptotic nuclei was evaluated within sacs that result from failed obliteration of PV. Materials and Methods: Twenty sacs associated with female inguinal hernia (n = 5), male inguinal hernia (n = 6), hydrocele (n = 5), hydrocele of the cord (n = 2), and undescended testis (n = 2) were evaluated. 10-mum sections were cut from the snap-frozen samples and stained for nuclear DNA fragmentation. Results: Apoptotic nuclei were detected within the vascular structures and mesothelium. However, none of the samples from different diagnostic sources have revealed any apoptotic nucleus within the smooth muscle component. Conclusions: While the vascular and mesothelial structures within the sacs reveal evidence of apoptosis, the smooth muscle component lacks apoptotic process. The failed apoptosis of smooth muscle may have a role in the persistence of PV. Copyright (C) 2002 S. Karger AG, Basel.