The aim of the study was to evaluation of succinic dehydrogenasein human semen samples. A total of 45 asthenozoospermiainfertile patients and 25 fertile males participated in this study.Immunocytochemical detection was used to localize succinicdehydrogenase (SDH) in the head & mid-piece of spermatozoaby fluorescent microscope. The study revealed dispersed SDHactivity in the semen of asthenozoospermic subjects in comparisonto control semen samples. While the stain intensity variedfrom cell to cell in controls as well as in patients, it was predominantlylocalized with in mid-piece of spermatozoa in healthyindividuals. In contrast, in semen of infertile male, the diffusedand dispersed SDH immuno-reactivity was observed in head aswell as in mid-piece region of spermatozoa. A comparison ofstaining intensity revealed negative, dispersed-mild, moderateand intense staining in 8.9%, 17.8%, 33.3% and 40% ofsperm cells asthenozoospermic males, respectively. Dispersedexpression of mitochondrial SDH in the sperm head & midpiece of human spermatozoa of infertile subjects is indicativeof mitochondrial damage due to metabolic or genetic factorsaffecting the energy production in the spermatozoa and may beresponsible for disturbed motility of spermatozoa incases of asthenozoospermia and thus could be pathologicallysignificant. Present investigation highlights need for detailedmitochondrial SDH immunolocalization studies to establish arole of deranged Krebs cycle in causation of male infertility.