The ampicillin coupling on BIOZAN R (a polysaccharide of microbial synthesis Xanthomonas campestris) is studied by the activation of carboxylic groups by dicyclohexylcarbodiimide. The following optimum reaction parameters are settled on the basis of an experimental program: time = 7.5 h, temperature = 10 °C, dicyclohexylcarbodiimide concentration = 1.10-3 mole, ampicilline concentration = 2.4·10-3 mol. Under these conditions up to 37% of ampicillin with respect to the polymer is coupled. The microbiological and hydrolysis studies under the conditions of the human physiological pH attest the ampicillin maintains its activity and may be released in oral administration.