The aim of this study was to determine the level of nitrite in post mitochondrial fraction of liver and the toxicity in liver and kidney of wistar rat. Forty two male wistar rats were divided into six groups and each group was with varying doses of sodium nitrite and N-methylaniline. The following methods were employed, spectrophotometric, cell fractionation, centrifugation, dialysis, histopathology and ultra violet irradiation. There was a significant increase (P < 0.05) in the level of nitrite in the post mitochondrial fraction of liver in all the experimental groups compared to the control. After exposure to UV-light there was a decrease in the level of nitrite in all the groups, which indicates that the UV-light has degraded the precursors of N-nitrosamine. The histopathology study showed severe haemorrhage within sinusoid, the portal triad was infiltrated by inflammatory cells within the sinusoid of the liver and kidney. The present study showed that the concentration of nitrite in the post mitochondrial fraction of the liver of the rat depends on the dose of the toxins. The study also showed UV degradation of precursors of Nnitrosamine and the effect of the toxins on both liver and kidney.