The stability of ceftriaxone disodium solutions stored in glass bottles was tested in two parenteral solvents (0.9% NaCl; 5% dextrose) at two concentration rates (10 and 50 mg/mL) and three temperatures (-22 degrees C, 5 degrees C, room temperature). The solutions, which had been initially frozen, were thawed at room temperature or by exposure to microwave radiations. The stability of each sample was determined by a quantitative bacteriological agar gel diffusion assay and by high-performance liquid chromatography. The results of this study indicate that admixtures of ceftriaxone disodium at the concentration rates tested can be frozen for six months without a significant loss in antibiotic activity. At room temperature, the stability is dependent on the concentration of ceftriaxone disodium. At 5 degrees C, the stability is related to the concentration of ceftriaxone and of the solvent. The results obtained by both analytical methods are very close. In order to perform routine assays, the high-performance liquid chromatography method was chosen on the basis of its rapidity and reproducibility.