Ultrastructural characteristics and meiotic segregation in spermatozoa from twelve patients affected by uro-genital bacterial infections were investigated. The sperm quality was examined by light and transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH) analysis was performed in eight out of twelve individuals in order to investigate the meiotic behaviour of chromosomes namely gonosomes and chromosome 18. TEM analysis highlighted a severely altered sperm morphology, typical of apoptosis and in particular, necrosis. We define the ultrastructural characteristics of necrosis as involving the acrosome, chromatin, mitochondrial helix, axonemal structure and plasma membrane. Based on our observations, it is possible to hypothesize that infection acts at the testicular level causing sperm death, due to necrosis itself or by necrosis proposed as the final step of apoptosis. Moreover, FISH analysis revealed the presence of altered meiotic segregation in these patients. The high rate of diploidy and gonosomes disomy in our group of patients suggests the possibility of a negative effect of infection and/or inflammation on sperm morphogenesis.