A high-pressure liquid chromatographic (HPLC) method was developed for the determination of residues of karbutilate (3-[ [(dimethylamino)carbonyl]amino]phenyl(l,l-dimethylethyl)carbamate), its hydrolysis product N'-(3-hydroxyphenyl)-N,N-dimethylurea and its demethylated metabolites monomethyl karbutilate (3-[ [ (methylamino)carbonyl)]amino]phenyl (1,l-dimethylethy1)carbamate) and demethyl karbutilate (3-[ (aminocarbonyl)amino]phenyl (1,l-dimethylethyl)carbamate), in water, soil, and grass. Recoveries of karbutilate and its degradation products from water ranged from 89 to 103%. The lower limit of sensitivity of the method is 0.01 ppm for karbutilate and N'-(3-hydroxyphenyl)-N,N-dimethylurea and 0.02 ppm for monomethyl karbutilate. The recovery of karbutilate and its carbamate metabolites from soil ranged from 84 to 95%. For residues in grass, the carbamates are converted to the corresponding phenols, which are analyzed by HPLC. The recovery of karbutilate and its carbamate metabolites from grass ranged from 80 to 87 7%. The lower limit of sensitivity of the method for residues in soil and grass is 0.1 ppm for karbutilate and 0.2 ppm for monomethyl karbutilate and demethyl karbutilate.