The apparent stability of combinations of hydroxyzine hydrochloride and meperidine hydrochloride (50 mg/2 ml each) and of these two drugs (50 mg/2.5 ml each) and atropine sulfate (0.4 mg/2.5 ml) in prefilled glass and plastic syringes was studied. Syringes (3 ml) containing the combinations were stored at 25 C and 3 C for 10 days and analyzed at specific time intervals. Absorption spectra, chromatographic characteristics and pH were determined in addition to visual inspection. Results of these qualitative tests indicated that the mixtures apparently were stable for 10 days at room temperature or when refrigerated. No differences were found between solutions stored in glass and those stored in plastic syringes. Degradation of the syringe contents or appearance of additional constituents was not detected in any of the admixtures, and they were considered to be chemically compatible within the limitations of the study. The study suggests that storage of these combinations in syringes is feasible but the results cannot be extrapolated to drug solutions or syringes other than those studied.