A reverse-phase HPLC system using a microparticulate octade-cylsilane column and an acetonitrile-phosphate buffer mobile phase is employed to determine lidocaine in an admixture of lidocaine injection with 5 per cent dextrose injection. The method is accurate over the range of 5 to 12.5 μg on column, as employed in our laboratories, which corresponds to 2 to 5 mg/ml of lidocaine hydrochloride in the admixture solution. It is precise (2.00 to 2.88% coefficient of variation) and has been used in stability studies of lidocaine. The method is also used to quantitate a degradation product of lidocaine, 2,6-dimethylaniline, over the range of 5 to 25 ng on column (corresponding to 2 to 10 μg/ml in the admixture solution) with a precision of 1.82 to 4.50% coefficient of variation. Samples are prepared by dilution in methanol containing the internal standard, procaine hydrochloride, and each chromatogram requires about 4 minutes.