Assay methods have been developed which are specific for the analysis of diazepam in the presence of formulation excipients, closely related degradation products and manufacturing impurities. The methods developed used difference ultraviolet spectrophotometry and HPLC. These methods have been applied to the analysis of diazepam in formulations and to investigate the reaction kinetics of the acid hydrolysis of diazepam. From analysis of both fresh and stored samples of formulations, it was seen that solid dosage forms showed no degradation, but degradation products were detected in liquid formulations. Advantages and disadvantages were seen for both techniques and criteria were established for the choice of method. The reaction kinetics of the degradation of diazepam was studied, using HPLC and GC. Previous workers had investigated the acid hydrolysis of diazepam using non-specific analytical methods. An attempt was made to repeat their work using the specific chromatographic methods described. From initial work, it appears that the results obtained are similar to those previously generated. Further work is required to investigate this more fully.