Sequential interpenetrating networks of poly(methacrylic acid) and poly(vinyl alcohol) have been prepared and cross-linked with glutaraldehyde to obtain pH sensitive microspheres by a water-in-oil emulsification method. Microspheres have been used to deliver the chosen model anti-inflammatory drug viz., ibuprofen to the intestine. Ibuprofen was encapsulated up to 70% within polymeric matrices. The interpenetrating polymer network formed was analysed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and X-ray diffraction analyses were done on drug-loaded microspheres to confirm the polymorphism of ibuprofen. Results of this study indicated the molecular level dispersion of ibuprofen in the developed microspheres. Scanning electron microscopy confirmed the spherical nature and smooth surfaces of the microspheres produced. Mean particle size of the microspheres as measured by laser light scattering ranged between 51-176 mu m. Swelling was performed in the simulated gastric as well as the intestinal conditions. Microspheres showed a pulsatile swelling behaviour when pH of the swelling media was altered. The swelling data have been fitted to an empirical equation to understand water transport trends as well as to calculate the diffusion coefficients. Values of diffusion coefficients in acidic media were lower than those found in the basic media. Values of diffusion coefficients decrease with increasing cross-linking of the matrix. In vitro release studies have been performed in 1.2 and 7.4 pH media to simulate the gastric and intestinal conditions. The in vitro release results indicated a dependence on the pH of the release media, extent of cross-linking and the amount of drug loading. The release data were fitted to an empirical relation to estimate the transport parameters and thereby to understand the transport mechanism.