The release rate of nicardipine HCl from various alginate gel bead formulations was investigated. The formulations were prepared by utilizing 2(3) factorial design. The effect of drug:polymer weight ratio, CaCl2, and sodium-alginate concentration on the time for 50% of the drug to be released (t(50%)) and the drug entrapment efficiency were evaluated with analysis of variance. The mean particle size and the swelling ratio of the beads were determined. The in vitro release studies were carried out by flow-through cell apparatus in different media (pH 1.2, 2.5, 4.5, 7 and 7.5 buffer solutions). Drug:polymer weight ratio and the interaction of drug:polymer weight ratio and CaCl2, concentration had a significant effect on the drug entrapment efficiency. The release of nicardipine was extended with the alginate gel beads, which were prepared in a ratio of 1:1 (drug:polymer). The release of drug from alginate gel beads took place both by diffusion through the swollen matrix and relaxation of the polymer at pH 1.2-4.5. However, the release was due to the diffusion and erosion mechanism at pH 7-7.5. (C) 1998 Elsevier Science BN.