Near-infra-red reflectance spectroscopy is used to determine the active ingredient concentration and water content of an antibiotic powder (ceftazidime pentahydrate). The validity of predictive models for active ingredient concentrations and water content, constructed by means of the multiple linear regression technique is discussed. A procedure is devised for the analysis of production samples, which, on account of the very limited range of concentrations, prove a difficult fit to the above-mentioned model. The results obtained in testing formulation samples from 1 year's industrial production are used to illustrate the potential of the technique.