Analytical methods were developed to determine cyclosulfamuron residues in soil, water, rice grain and straw using high-performance liquid chromatography (HPLC) with ultraviolet absorption detection. In these methods, cyclosulfamuron was extracted with aqueous Na₂HPO₄/acetone and acetone/methanol mixture from soil and rice samples respectively. Liquid-liquid partition coupled with ion-associated technique, Florisil column chromatography, and solid-phase extraction (SPE) were used to separate cyclosulfamuron from interfering co-extractives prior to HPLC analysis. For water sample, the residue was enriched in C_(18)-SPE cartridge, cleaned up in situ, and directly subjected to HPLC. Reverse-phase HPLC under ion-suppression was successfully applied to determine cyclosulfamuron in sample extracts with the detection at its λ_(max) (254 nm). Recoveries from fortified samples averaged 87.8±7.1% (n=12), 97.3±7.2% (n=12), 90.8±6.6% (n=6), and 78.5±6.7% (n=6) for soil, water, rice grain and straw, respectively. Detection limits of the methods were 0.004 mg/kg, 0.001 mg/L, 0.01 mg/kg and 0.02 mg/kg for soil, water, rice grain and straw samples, respectively.