The stability of ceftazidime sodium and teicoplanin sodium separately and in combination in a peritoneal dialysis (PD) solution was studied. PD solutions containing ceftazidime 100 micrograms/mL (as the sodium salt), teicoplanin 25 micrograms/mL (as the sodium salt), or ceftazidime 100 micrograms/mL plus teicoplanin 24 micrograms/mL were prepared in triplicate for each of two conditions: condition A, storage at 25 degrees C (room temperature) for 24 hours, then at 37 degrees C for eight hours; and condition B, storage for seven days at 4 degrees C, followed by 16 hours at 25 degrees C and 8 hours at 37 degrees C. The dialysis solution used was Dianeal PD-2 with 1.5% dextrose. Samples were removed at intervals and analyzed by stability-indicating high-performance liquid chromatography. Under condition A, ceftazidime sodium alone was stable for 24 hours at 25 degrees C but only 2 hours when then heated to 37 degrees C. Under condition B, ceftazidime sodium alone was stable throughout the observation period. Teicoplanin sodium alone was stable throughout the observation periods under both conditions. In combination, the drugs were stable if initially refrigerated and then brought to room temperature one week later, but were unstable when initially stored at 25 degrees C. No visual changes were noted, and pH did not vary substantially. Ceftazidime 100 micrograms/mL (as the sodium salt) and teicoplanin 25 micrograms/mL (as the sodium salt) combined in a PD solution were unstable when first kept at 25 degrees C before storage at 37 degrees C. The drugs in the combination remained stable when the solution was kept at 4 degrees C before storage at 37 degrees C.