A sensitive and specific method for the quantitative determination of the new drug, almitrine bismesylate, was developed based on the procedure reported by Baune et al. The method depends on initial extraction of drug from plasma with cyclohexane followed by separation from acidic constituents by a base wash. Final separation and quantitation of almitrine was achieved by GLC with NPD detection using the dtmethyl derivative (S-2082) as internal standard. The method was shown to be specific for almitrfne and for internal standard by a parallel run using GC/MS and anaiysis of the M.S. species. The procedure was linear from 25 to 175 ng/ml. Assays were routinely performed with 1 ml of plasma though the analysis could be performed with 0.5 ml. The method is rugged, having been run by at least three analysts over a span of more than 5000 samples, and efficient, allowing 60 samples per day throughput on a routine basis.