The solid-state properties, dissolution profile and antimicrobial activity of inclusion complexes of cefdinir (CEF) with beta-cyclodextrin (betaCD) and hydroxypropyl beta-cyclodextrin (HPbetaCD) were investigated. The phase solubility profiles of cefdinir with betaCD and HPbetaCD were classified as A(L)-type, which indicates the formation of 1:1 stoichiometry inclusion complexes. Stability constants with 1:1 molar ratio obtained from the phase solubility diagrams were 120.38+/-1.07 and 58.60+/-1.20 M(-1) for betaCD and HPbetaCD, respectively. Binary systems of CEF with betaCD and HPbetaCD prepared by kneading method were characterized by Fourier transformation-infrared spectroscopy (FTIR) and X-ray powder diffractometry (XRD). The aqueous solubility of CEF was enhanced by 101% for betaCD and 23.4% for HPbetaCD, respectively. The dissolution profiles of inclusion complexes were determined and compared with those of CEF alone and their physical mixtures. The dissolution rate of CEF was increased by betaCD and HPbetaCD inclusion complexation moderately. However, the antimicrobial activity of CEF was increased significantly (p<0.001) by betaCD and HPbetaCD inclusion complexation against S. aureus and E. coli. In all these studies, HPbetaCD had superior antimicrobial activity than that of betaCD while betaCD had greater effect on solubility enhancement of CEF.