Abstract The characteristics of chlorpyrifos was studied to clarify the effect of the cultivation season,spray intervals, spray volume and concentration on residues in chilli and sweet peppers cultivated undergreenhouse condition. Residue levels of chlorpyrifos detected in chilli pepper fruit cultivated were 1.5 to 2.7times higher in winter(February-March) than those in summer(June-July). During winter season residue levelsof chlorpyrifos in chilli peppers were 6.9~3.2 times higher than those in sweet peppers for 10 days after 3times application with 7 days interval. Residue levels in chilli pepper were from 2.070 mg/kg at 1 day to0.929 mg/kg at 10 day, while those in sweet pepper were from 0.302 mg/kg to 0.291 mg/kg. Residue levels insweet pepper to which are 3 times applied with 7 days interval were from 0.302 mg/kg at 1 day to 0.291 mg/kg at 7 day, and the residue levels in sweet pepper which are 3 times applied with 3 days interval were from0.498 mg/kg at 1 day to 0.470 mg/kg at 7 day. Residue levels of chlorpyrifos in the sweet peppers applied bydouble concentration were 2.5 times higher than those sprayed by normal standard amounts diluted in doublevolume. Key words Chlorpyrifos, Sweet pepper, Chilli pepper, Pesticide residue