Diazinon is a chemical pesticide used for a wide range of agricultural and horticultural crops. However, its residue in agricultural products could seriously threaten human health. The present study measured diazinon residue in tomato, cucumber and melon by collecting samples from differentareas including 2 regions for tomato (Mashhad and Shiravan), 6 regions for cucumber(Disfool, Jiroft, Kerman, Shirvan, Torbate-Jam and Mashhad), and 2 regions for melon (Shiravan and Torbate-Jam). Diazinon residues were determined using gas chromatography (GC) technique. Results showed that pesticide residue in melon samples from Torbate-Jam and Shiravan were 4.98 and 4.11 times more than the permited residue level, respectively. Cucumber samples collected from Disfool,Rafsanjan, Jiroft, Kerman and Shiravan were 6.1, 4.4, 4.2, 2.1, and 1.8 times higher than the permitted level, respectively. However, diazinon residue in cucumber and tomato grown in Mashhad were lower than permitted levels.