An experimental study was conducted to determine the quantity of contamination of organophosphrous pesticides accumulated in each human tissues. The samples used for this experiment were spleen, lung, heart, liver and kindney and those tissues were homogenized by a blender. The homogenized materials was extracted with mixed solvent, acetone/benzene (1:1) and cleaned up on a activated carbon column and determined by gas chromatography using AFID supported on 5% QF-1. The average recovery rate was 94% and the results obtained are summarized as follows. 1) The quantities of Malathin accumulated in each tissues were 0.53 ppm in spleen, 0.42 ppm in lung, 0.34 ppm in kidney, 0.19 ppm in heart and 0.19 ppm in liver. 2) Residues of pesticides in chronic or acute intoxicated tissues were highest in the spleen, decreasing in order of the lung, kidney, heart, and liver. 3) According to the above resuk we can conclude that the most proper material in detecting the pesticide is the spleen.