Partition coefficients, determined for the aqueous/acetone solution - dichloromethane system, ranged from 40 to 100, and indicated that the losses of the twenty two tested pesticides, potentially resulting from incomplete extraction procedure, should not exceed 1% and may well be disregarded as the possible cause of error. The recoveries of individual pesticides from spiked samples, using a single extraction with dichloromethane, were within a narrow range of 80 to 90% with Relative Standard Deviations not exceeding 5-6%.