Interpenetrating polymeric network microspheres (IPNMs) consisting of poly(vinyl alcohol) and sodium carboxymethylcellulose were prepared by water-in-oil emulsion method and were cross-linked with glutaraldehyde. 5-Fluorouracil (5-FU), an anti-cancer drug, was loaded into IPNMs via in situ method. These IPNMs have been characterized by Fourier transform infrared spectroscopy, which confirms the cross-linking of IPNMs through glutaraldehyde. Differential scanning calorimetry and X-ray diffraction analysis of the drug-loaded IPNMs have confirmed uniform molecular dispersion of 5-FU in the IPNMs. Particle size measured using optical microscopy gave an average size of 80-250 mu m. Scanning electron microscopy also confirmed the formation of microspheres with smooth surface and spherical shape. Encapsulation efficiency of 5-FU in these IPNMs was achieved up to 62%. Drug release profiles of the IPNMs at different pH conditions (pH 1.2 and 7.4) confirmed that microspheres formed are pH sensitive, resulting controlled release of drug during in vitro dissolution experiments. It has been analyzed with an empirical equation to understand the diffusion nature of drug through the IPNMs. Both encapsulation efficiency and release patterns are found to depend on the nature of the cross-linking agent as well as amount of drug loading. In vitro release studies indicated the release of 5-FU for more than 10 h.