The presence of ten organophosphorus pesticides was studied in tomatoes acquired from markets in Bogota (Colombia), using Liquid-liquid Extraction (LLE) and High Resolution Gas Chromatography (HRGC) with flame photometric detector (FPD). The pesticides analyzed were: Chlorfevinphos, Chlorpyrifos, Demeton O, Demeton S, Dichlofenthion, Dimethoate, Famphur, Leptophos and Trichlorfon. Eighteen samples were analyzed in which fifty five percent were contaminated with Dimethoate. Dimethoate levels in the contaminated samples were below the maximun residue levels (MRL) of 1 mg/kg established by the Codex alimentarius. Residues of Methyl parathion and Chlorfevinphos were also found, below the MRL.