Praziquantel was determined by gas–liquid chromatography (GLC). The determination was based on the concept of internal standardization; papaverine was used as the internal standard. Five independent analyses of two samples containing 0.105 and 1.370 mg cm–3 of praziquantel showed relative standard deviations of 0.540 and 0.155% respectively. The minimum detection limit of the GLC method was found to be 0.5 µg mm–3 of praziquantel. The GLC method was successfully applied to the determination of praziquantel in commercially available biltricide tablets. As a check on the accuracy of the GLC method, control experiments were carried out on biltricide samples by addition of known amounts of praziquantel and ascertaining the recoveries. The results were reproducible and quantitative. The results obtained by applying the GLC method to the determination of praziquantel in biltricide tables were compared with those of a derivative spectrophotometric method. Statistical analysis of the results revealed good correlations between the two methods. However, the GLC method was found to be more sensitive and accurate than the derivative spectrophotometric method.