Background and Objectives: The most common problems limiting the medical use of aminoglycosides have been the nephro- and oto-toxicities as well as the increasing bacterial resistance. Encapsulation of drugs into liposomes enhances their efficacy while reducing their toxicities. The aim of this study was to evaluate the antimicrobial activity of free and liposomal amikacin. Material and Methods: Encapsulated amikacin into liposome was prepared by sonication. The drug contained in the liposome was measured by HPLC after lysis of vesicles by 0.2% Triton X-100. The amikacin kinetic released from liposomes in the presence of normal human pooled plasma was also evaluated. The MICs of this drug for Pseudomonas. aeruginosa (ATCC 27853), Escherichia. coli (ATCC 25922), Streptococcus. faecalis (ATCC 29212) and Staphylococcus. aureuse (ATCC 29213) were determined and compared to those of the respective free drug using a broth dilution method. Results: In the presence of plasma, liposomal retention of amikacin was 80.25 ± 0.55% (P ≤ 0.05) after 1 h of incubation and then remained nearly constant over a 24 h period of the study. The encapsulation efficiency of liposomal preparation was 24.36% ± 0.14 (P ≤ 0.05) of the initial amount of the drug in solution. The MICs of liposomal amikacin against all bacterial strains tested were lower than MICs of free amikacin. Conclusion: The amikacin appears a promising approach in the management of bacterial infections and should be further evaluated in vivo experiments.