The purpose of this study was to assess the effects of lead administration on the kidney and testicular structure of adult rats. Rats received lead (PbNO(3)) in single intraperitoneal dose 50 mg/kg (group A), 25 mg/kg (group B) and 12.5 mg (group C) per kilogram of body weight and were killed 48 h following lead administration. After the preparation of histological samples the results were compared with control. After the lead administration dilated Bowman's capsules and blood vessels in interstitium of kidney with evident hemorrhagic alterations were noted. Quantitative analysis determined increased relative volume of interstitium and tubules. Also, the diameter of renal corpuscules, diameter of glomeruli and diameter of Bowman's capsule were significantly increased, especially in group A, with the highest lead concentration. In testes, dilatation of blood capillaries in interstitium, undulation of basal membrane and occurrence of empty spaces in seminiferous epithelium were detected. An apoptosis assay confirmed increased incidence of apoptosis in the spermatogenetic cells after the lead administration. Also further morphometric analysis showed significant differences in evaluated parameters between control and treated groups. The number of cell nuclei was decreased in lead-treated groups, which is concerned with the occurrence of empty spaces as well as with the higher apoptosis incidence in germinal epithelium. This study reports a negative effect of lead on the structure and function of kidney and testes.