A simplified high-performance liquid chromatographic procedure is described for the determination of furosemide (4-chloro-N-furfuryl-5-sulphamoylanthranillic acid), which makes use of UV detection, a C18, reversed-phase column, and micellar mobile phases of sodium dodecyl sulphate (SDS) and 1-propanol at pH 3 buffered with phosphate system. The most adequate experimental conditions to handle furosemide solutions in the analytical laboratory are studied. The mixture of furosemide and its degradation products which are formed upon light exposition was resolved with a mobile phase of 0.04 M SDS-2% propanol. Separation of furosemide from its common impurities and the hydrolytic product, 4-chloro-5-sulphamoylanthranillic acid, was also possible. A mobile phase of larger elution strength, such as 0.06 M SDS-8%, propanol was preferred to assay furosemide in several dosage forms (tablets, capsules, injectables and drops). The validity of the procedure was checked by analysing 27 pharmaceuticals commercialised in several countries. The label claim percentages and coefficients of variation were in the 95-102% and 0.05-1.3% ranges, respectively. The results showed that the procedure is suitable for routine analysis of the diuretic.