The compatibility of tropisetron (pure undiluted 1 mg mL(-1) and diluted with 5% glucose or 0.9% NaCl (saline)) with glass, poly(vinyl chloride), polypropylene or polyethylene containers has been studied over a period of two weeks. The drug solutions were exposed to different light and temperature conditions. Tropisetron was assayed by high-performance liquid chromatography. The results show that undiluted tropisetron is stable in polypropylene syringes for two weeks under all the storage conditions tested (daylight at room temperature, dark at room temperature, refrigerator at 4 degrees C). Some variations in concentration were observed after dilution of tropisetron but these remained within 10% of the initial concentration. Tropisetron can be stored undiluted at 1 mg mL(-1) in polypropylene syringes, although it is preferable to perform dilutions extemporaneously. Tropisetron diluted with 5% glucose or saline can be kept equally well in glass, poly(vinyl chloride) (Travenol bags) or polyethylene (ecoflac) containers.