The physical and chemical stability of fenoldopam as the mesylate salt were studied. Test samples of fenoldopam mesylate, with fenoldopam concentrations ranging from 4 to 300 micrograms/mL, were prepared in polyvinyl chloride (PVC) bags of 5% dextrose injection and 0.9% sodium chloride injection and were stored at 4 degrees C in the dark and 23 degrees C in ambient fluorescent light. Physical and chemical stability were evaluated at 0, 24, 48, and 72 hours. Physical stability was assessed by visual observation in fluorescent light and using a high-intensity monodirectional light beam. Turbidity and particle content were measured electronically. Chemical stability of fenoldopam mesylate was evaluated by using a stability-indicating high-performance liquid chromatographic analytical technique. All samples were physically stable throughout the study. Little or no change in particulate burden and haze level was found. Little or no loss of fenoldopam occurred in concentrations of 40 micrograms/mL or greater at either temperature throughout the study period. At the lowest concentrations, minor losses of 3-5% were found. Fenoldopam mesylate, prepared in fenoldopam concentrations ranging from 4 to 300 micrograms/mL, was physically and chemically stable in PVC bags of 5% dextrose and 0.9% sodium chloride injections for 72 hours when stored at 4 degrees C in the dark and 23 degrees C when exposed to ambient fluorescent light.