Introduction: Inguinal hernia and hydrocele are suggested to result from the persistence of smooth muscle (SM) which should undergo programmed cell death (PCD) after presenting transiently to propel the testis. Since Ca2+ is involved in PCD, the Ca2+ contents of the peritoneum and sacs associated with undescended testis, inguinal hernia and hydrocele were determined and compared. Materials and Methods: Sacs were obtained from boys with undescended testis (n = 11), inguinal hernia (n = 22) and hydrocele (n = 10), and girls with inguinal hernia (n = 7). The calcium content of the sacs and peritoneal samples (n = 6) was determined through atomic absorption spectrophotometry. Calcium contents were compared according to their sources using the Mann-Whitney U test and p values of <0.05 were considered significant. Results:While revealing similar Ca2+ contents as the peritoneum, sacs associated with undescended testis and hydrocele contained more Ca2+ contents than the sacs of boys and girls with inguinal hernia (p < 0.05). Conclusions: Sacs associated with inguinal hernia, which are known to contain SM all around the mesothelial layer, contain the least Ca2+. Despite the decrease in SM, sacs associated with hydrocele contain more Ca2+. Since PCD is associated with Ca2+ overload and inhibition of Ca2+ load inhibits PCD, differences in Ca2+ content may reflect the inhibition of PCD at different stages and for different reasons in inguinal hernia or hydrocele of childhood. Copyright (C) 2003 S. Karger AG, Basel.