AbstractA laboratory‐assembled high pressure liquid chromatograph with variable wavelength ultraviolet detector is described. The chromatography of the systemic fungicides benomyl, thiabendazole, thiophanate, related fungicides and benzimidazoles (13 compounds in all) is described using reverse phase and adsorption systems. Temperature affects reverse phase systems but not adsorption systems. Use of a variable wavelength detector increases sensitivity and selectivity. High pressure liquid chromatography (h.p.l.c.) has been applied to measurements of the solubility of benomyl and carbendazim in water and the degradation of benomyl in solution. Use of h.p.l.c. to measure benzimidazole residues awaits the development of methods of avoiding interference by substances extracted from crops and soils.