A multiresidue analytical method based on C18 solid-phase extraction and one-run HPLC determination has been developed for the analysis of eleven acidic, neutral and weak basic herbicides in drinking water. A 1-1 sample of water was preconcentrated by passage through a 500-mg C18 solid phase extraction column. The retained compounds were eluted from the column with 1 ml of methanol. After concentration of the extract the pesticides were separated and quantified by reversed-phase HPLC with UV detection. Bentazone, 2,4-D, MCPA, fluazifop-acid, metoxuron, monolinuron, metobromuron, diuron, linuron, atrazine and simazine were determined simultaneously in a single run on a C18 HPLC column. Reanalyses of the sample extracts on a second cyano column were used to confirm the identity of the neutral and basic compounds. The limit of determination, defined as four times the baseline noise, varied between 0.01 microgram/l and 0.1 microgram/l depending on the compound, the detection sensitivity of the instrument and the type of HPLC column used.