The primary and secondary objectives of this study were to develop and evaluate the predictability of in vitro-in vivo correlation models for theophylline sustained release (SR) granules. Theophylline SR granules meeting the USP Drug Release Test criteria were prepared using ethyl cellulose (EC) and/or stearyl alcohol (SA) and the wet granulation method. In vitro dissolution studies of granule formulation were performed, and a commercial dosage form was prepared using USP XXIII apparatus II at pH 4.5. Differences and similarities between in vitro dissolution curves were compared using both model-dependent (t-test) and independent (f(1), f(2) test) statistical techniques, and it was shown that the three dissolution profiles i.e model-de pendent, model-independent, and methods based on ANOVA were very similar. The in vivo performance of the commercial dosage form was tested by oral route using male rabbits and in vitro-in vivo correlations were established.