Pollution of water sources by pesticides is a result of intensive use of these compounds, and the establishment of analytical methods for monitoring programs is very important. This paper presents a method for the determination of multiclass pesticide residues in rice paddy water based on SPE and GC/MS/MS. The validation results were satisfactory. All compounds showed adequate linearity (r2 >or= 0.99), and analysis by GC/MS/MS with a triple quadrupole mass spectrometer gave high selectivity and sensitivity. With the proposed SPE step an LOD of 0.06 microg/L was achieved. Recoveries from blank samples spiked at 0.2, 04, and 0.8 microg/L were between 70 and 120% with RSD <20% for most analyzed compounds, despite their different chemical nature, indicating good accuracy and precision. The proposed method is efficient for pesticide residue determination, including some metabolites, and gave good performance when applied to real samples.