Toxicity of cadmium may hurt the reproductive system at lower doses that necessary for produce nocive effects in the rest of the tissues. Cd (10 mg/L as cadmium acetate) was administered as drinking water to Wistar rats from day 1 of pregnancy to delivery. At birthday (0 pp) or after 5 days (5 pp), pups were sacrificed, and testis were removed, weighed and frozen for study the alterations in proteins content and total nucleic acids. Some testis were used for histology; the diameter of seminal tubuls was measured and the number of prospermatogonia was counted.The results show a significant reduction in the weight of testis, due to the intoxication of cadmium. The DNA content decreased, and so the ratio DNA/RNA. One possible explanation for this reduction in nucleic acids can be the inhibition of the timidine kinase activity (1). As the RNA was not modified, the lower proteins amount can not be due to the alterations in the traductional process, but might be due to the lost of ribosomes joined to the membrane of endoplasmic reticle, responsible of the proteins sinthesis descrited in Cd intoxication. We found also a significant decrease in the diameter of seminal tubuls (μm) (Control 0: 49.2 ± 4.6; Cd 0: 18.1 ± 2.3; Control 5: 53.9 ± 3.6: Cd 5: 22.7 ± 3.4) and the number of prospermatogonia (Control 0: 13.0 ± 1.7; Cd 0: 11.2 ± 1.2; Control 5: 13.7 ± 1.5; Cd 5: 12.6 ± 1.4).