Functionalized polymers have gained much interest in the last decades. This is due to their functional groups and their polymer nature, which give them unique properties and more advantages than the corresponding small molecules. In this trend, we modified polyacrylamide by introducing an amino group in the side chain of the polymer by reacting it with ethylenediamine. The aminemodified polymer was reacted with two classes of active compounds. The first group is aromatic aldehydes containing active groups such as p-hydroxybenzaldehyde, vanillin, p-chlorobenzaldehyde, and anisaldehyde. The second group is phenolic ester derivatives such as p-hydroxymethylbenzoate, 2,4-dihydroxymethylbenzoate, 2-hydroxymethylbenzoate and 3,4,5-trihydroxypropylbenzoate. The antimicrobial activity of these two classes were explored by cut plug method against Candida albicans SC5314, Aspergillus flavus, and Fusarium oxysporium as fungal organisms and Bacillus subtilis, Escherichia coli, and Staphylococcus aureus as bacterial organisms. It was found that the diameter of inhibition zone varied according to the active group in the modified polymer and the examined microorganism. In general, the modified polymers showed antimicrobial activity against the tested microorganisms. However, the polymer derivative of p-chlorobenzaldehyde being the most effective on bacteria and fungi species. (c) 2005 Wiley Periodicals, Inc.