Cefuroxime sodium (Zinacef) is a new semisynthetic, broad spectrum cephalosporin antibiotic for parenteral administration which is stable to most of the beta-lactamases. The stability of cefuroxime sodium in aqueous solutions, with or without phosphate buffer, and in 5% dextrose and 0.9% sodium chloride injections was studied using a stability-indicating high-pressure liquid chromatographic method developed in our laboratory. The optimum pH range of stability was determined to be approximately 4.5-7.3. Both buffered and unbuffered solutions followed first-order decomposition. In 5% dextrose and 0.9% sodium chloride injections, cefuroxime was stable for 1 day (more than 90% potent) at 25 degrees C and for at least 30 days at 5 degrees C. At -10 degrees C, there was negligible decomposition after 30 days. The pH values of the solutions stored at 5 degrees C and -10 degrees C remained in the maximum stability range and the solutions were clear even after 30 days of storage. Thawing the frozen solutions in a microwave oven adversely affected the stability.