In addition to an increase in contractility, contracted fibers and small and electron-dense mitochondria have suggested an increase of cytosolic Ca2+ within the cremaster muscles (CM) associated with undescended testis. Therefore, the Ca2+ content of CM associated with an undescended testis was determined and compared with the Ca2+ content associated with inguinal hernia and hydrocele and in internal oblique muscles. CM samples from boys with undescended testis (n = 9), inguinal hernia (n = 15), and hydrocele (n = 7) and from girls with inguinal hernia (n = 8) were obtained. The calcium contents of these samples and of samples from internal oblique muscle (n = 6) were determined by atomic absorption spectrophotometry. While the Ca2+ contents of CM from boys with undescended testis and from girls with inguinal hernia were similar (p > 0.05), the internal oblique muscle and the CM from boys with inguinal hernia and hydrocele contained more Ca2+ than CM from boys with undescended testis (p < 0.05). Despite evidence of an increase in cytosolic calcium, the decrease in total calcium content suggests a decrease in the adenylyl cyclase activity, thus inhibition of influx of Ca2+, but an increase in phospholipase C activity, and generation of more inositol 1,4,5-trisphosphate and mobilization of calcium from internal stores. Since the sympathetic system acts through adenylyl cyclase in striated muscles and is sexually dimorphic, similar Ca2+ contents as encountered in girls suggest an alteration in the balance of autonomic innervation against the sympathetic system in boys with undescended testis. Copyright (C) 2002 S. Karger AG, Basel.