A stability-indicating HPLC method with diode array detection for the determination of paricalcitol, a synthetic vitamin D2 analog, was developed. Analytical parameters were studied according to International Conference on Harmonization guidelines. A C18 column (250 x 4.6 mm, 5 microm particle size) maintained at 25 degrees C was used as the stationary phase, and acetonitrile-water (70 + 30, v/v) as the mobile phase. Chromatograms were recorded at 250 nm. In forced degradation studies, the effects of acid, base, oxidation, temperature, and UV light were investigated and showed no interference with the drug peak. The method was found to be linear (r = 0.9989) at concentrations ranging from 0.6 to 10.0 mg/L paricalcitol, precise (repeatability and intermediate precision estimated as RSD less than 3.5%), accurate (recoveries higher than 95%), specific, and robust. The LOD and LOQ were 0.6 and 0.2 mg/L, respectively. The validated method was used for paricalcitol determination in a formal stability study of its pharmaceutical dosage form in preloaded syringes. The stability of a diluted solution of its pharmaceutical form in Viaflo bags was also tested. The results showed that paricalcitol was stable in preloaded syringes during a period of 30 days from preparation in the different storage conditions tested (room temperature without protection from daylight and 4.4 degrees C with protection from daylight). On the contrary, paricalcitol was quickly lost when stored in Viaflo bags by adsorption onto the walls of the container.