This study concerns the improvement in the antimicrobial activity of new aminated chitosan derivatives. p-Benzoquinone (PBQ) conjugated chitin was first prepared and then reacted with ethylenediamine (EDA) to get aminated chitin. The latter was finally deacetylated to get new aminated chitosan derivatives. Factors affecting conjugation and amination steps were studied. The amination process was confirmed by using FT-IR, TGA analysis, and the solubility test. The new aminated chitosan derivatives show a higher solubility, almost double, at a pH ranging from 5 to 6 compared with z pristine chitosan. The antibacterial activity of the chitosan derivatives was tested against four different bacterial strains: two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive (Bacillus cereus andStaphylococcus aureus). It was found that the antibacterial activity of the chitosan derivatives is better than those of chitosan and increases with the increasing amount of introduced amine groups. Furthermore, the cytotoxicity test using the Caco 2 cell line shows a moderate safety level for the new aminated chitosan derivatives. Chitosan derivatives show potential bactericidal activity against all strains examined especially against Gram-negative bacteria (E. coli and P. aeruginosa). For Gram-positive bacteria, chitosan derivatives killed 93% of B. cereus and 92% of S. aureus, compared with 44% and 85% for chitosan after 3 and 5 h, respectively. (C) 2011 Wiley Periodicals, Inc. Adv Polym Techn 31: 414428, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20264