These studies were carried out to investigate the residual behavi­our of fenitrothion and chlorpyrifos-methyl organoghosphorus insecti­cides on sugar-beet (vegetative parts and roots) and the contamination of soil under these plants. The residue half-life values (RL₅0) deter­mined on vegetative parts and soil were 16.8 and 134.4 hours for feni­trothion and 14.4 and 118.8 hours for chlorpyrifos-methyl, respectively. In vegetative parts, the initial amount detected for fenitrothion (28.843 ppm) was higher than the initial amount found for chlorpyrifos­methyl (5.170 ppm), while the initial concentration detected in sugar-beet roots was very low (0.012 ppm and 0.019 ppm) for fenitrothion and chlorpyrifos-methyl, respectively. The vegetative parts did not have any detectable residues of fenitrothion and chlorpyrifos-methyl at 16 days from application. No detectable amount of fenitrothion and chlor­pyrifos-methyl residues were found in the roots after 9 days from treat­ment. Fenitrothion and chlorpyrifos-methyl were found to be short per­sistent in the vegetative parts, but they were more stable in the soil.