The present study aimed to investigate the macro- and the microscopic structure of femoral bone tissue in adult male rats after selenium (Se) and simultaneous exposure to Se and Diazinon (DZN). One month-old male, Wistar rats were randomly divided into three groups, of 10 males each. In the first group (EG1), rats were administered by Se at a dose of 5 mg of Na2SeO3/l in drinking water for 90 days. In the second group (EG2), animals received a drinking water containing 5 mg of Na2SeO3/l and 40 mg of DZN/l for the same time period. The third group of males without Se and DZN administration served as a control group (CG). Our results revealed a significant decrease in femoral length and cortical bone thickness in experimental groups (EG1, EG2) of rats compared to the control ones (CG). Rats from experimental groups (EG1, EG2) also displayed different microstructure in the middle part of the femur, where vascular canals expanded into central area of the bone while, in control rats, these occurred near endosteal surfaces only. Additionally, a smaller number of primary and secondary osteons was identified in experimental groups of these rats. A few resorption lacunae were observed in them simultaneously administered to Se and DZN. Based on these findings we can conclude that sub-chronic exposure to Se and simultaneous exposure to Se and DZN influences significantly macro- and microscopic structure of femoral bone tissue in adult male rats