An attempt was made to apply high-performance liquid chromatography (HPLC) to a high-accuracy determination of linear alkylbenzenesulfonates (LAS) contained in environmental samples highly contaminated with organic matters; LAS was converted into chlorides (LAS-Cl) or methyl esters (LAS-O-Me) before being subjected to HPLC. The present HPLC method employed Shimadzu PC8-10, Waters micro Bondapak C18, or Jascopack SC-01-125 as a separating column, 85-90% methanol as an eluent, and wavelengths 250 and 225 nm for the measurement of LAS-Cl and LAS-O-Me, respectively. An experiment on material recovery for river water, sediment, and living body samples has given a satisfactory result that recovery is over 90%, coefficient of variation is 2-3%, and detection limit is 0.05 micro g. Test analyses have proved the present HPLC method to give rise to few interfering peaks so as to be satisfactorily applicable on actual environmental samples.