The degradation rates and residue levels of diazinon, pirimiphos‐methyl and chlorpyrifos in the leaves and fruits of pepper plants grown in commercial greenhouses were studied using g.l.c. Analysis of leaves at intervals following application showed that the initial residue of diazinon was higher than that of the other two insecticides, while its dissipation rate was faster. The dissipation of chlorpyrifos in fruits was faster than diazinon. The maximum residue levels (m.r.l.) of diazinon (0.5 mg kg−;1) and chlorpyrifos (0.1 mg kg−;1) were reached after 13 and 8 days of application respectively. With diazinon and pirimiphos‐methyl, sprayed 3 weeks before inflorescence, very low concentrations of both insecticides were found in fruits, although these compounds have no systemic behaviour. Chlorpyrifos residue level of 0‐2 mg kg −;1 in harvested fruits did not drop below m.r.l. after 11 days holding period.