Coupling of tetracycline (Tc) to dithiocarbamate chitosan(DTCC) via chelate bond was carried out in the presence of Mg (II) ion by one- and two-bath process. In one-bath process, DTCC was treated with Mg(II)-Tc solution. In two-bath process, DTCC was treated with Mg(II) to produce DTCCMg(II), which was isolated and treated in turn with Tc solution. The effect of pH and temperature on binding of Tc, was investigated varying the pH of the solution from 2.6 to 3.2 at 10 and $30^{circ}C$. Binding of Tc was not affected greatly by such variations in pH and temperature. Amount of Tc bound to 1 gm of matrix reached to 180 mg. Release of Tc from DTCC-Mg(II)-Tc was investigated by batch and flow method, and the amount of Tc released against time followed by flow method exhibited near linear relationship. DTCC-Mg(II)-Tc showed very prolonged antimicrobial activity compared to that of free Tc when it was tested against Escherichia coli TG-1 and Bacillus subtilis NA-1.