Two novel organopolyphosphazenes viz., poly[bis(4-methoxy benzylamino)polyphosphazene] (POP-1) and poly[bis(4-methoxyphenethylamino)polyphosphazene] (POP-2) have been synthesized by replacing chlorine atoms of polydichloro-phosphazene with 4-methoxybenzylamine and 4-methoxyphenethylamine. These polymers have been characterized by FTIR, H-1, C-13 and P-31 NMR. Polymers prepared have been subjected to DSC and TGA analysis to determine their glass transition temperature and thermal stability. Microspheres have been prepared by incorporating indomethacin (water insoluble) and 5-fluorouracil (water soluble) drugs. In vitro release characteristics of indomethacin was performed in 7.4 pH media, while for 5-fluorouracil, release studies were performed in both pH 7.4 and 1.2 buffer media. The % cumulative release of indomethacin increased with increasing drug loading. Sustained release was achieved at lower loadings of indomethacin. but for 5-fluorouracil, release was achieved in pH 1.2 media and the release was fast in pH 7.4 buffer media. (c) 2006 Elsevier B.V. All rights reserved.