Coriander, fennel and geranium plants were treated in the field with malathion (57% E.C) at the rate of 712.5 g active ingredient per feddan. Residue analysis showed that the initial deposits determined one hour after application were 16.51, 4.18 and 51.10 ppm on and in cori-ander, fennel and geranium plants, respectively. The residual rates of loss were 11.20, 57.18 and 28.32%, one day after treatment, respec‌tively. The amounts detected in the plants 21 days post application were 0.67, 0.001 and 0.30 ppm, respectively. The malathion residue half lives on these plants were 55.2, Z0.4 and 74.4 hours, respectively. Data of thin layer chromatograms indicated that parent com-pound malathion was detected in all samples of coriander and geranium throughout the experimental period, but far fennel samples it was de‌tected up to the 6th day. Four, five and one metabolites were detected in coriander, fennel and geranium samples, respectively. Malathion treatments increased essential oil contents in coriander and fennel plants by 10 and 15%, respectively. The mature dry seeds collected from coriander and fennel plants were devoid of any detectable amounts of malathion and its metabo‌lites. This indicates that such seeds could be marketed safely for human consumption.