Abstract: Nifedipine has been incorporated into Eudragit RL microspheres by the emulsionsolvent-evaporation process using an acetone/ liquid paraffin system,The drug in the Eudragit RLmicrospheres was present in either molecular dispersion or amorphous state.The drug release profilefrom microspheres confoimed to the Higuchi equation,The microspheres were stable under differentstorage conditions for six months with respect to drug content,dispersing state and release profile。The in vivo results in eight healthy volunteers showed that the relative bioavailability of the nifedipinesustainecl release microspheres against commercial retard tablet as a control was 102.5%,and themicrosphere fonnulation was bioequivalent to the retard tablet.Significant in vitro and in vivocorrelation was also found for the microspheres.