OBJECTIVE To explore the protein profile and identify developmentally regulated proteins of the promastigotes and axenic amastigotes with comparative proteomics technique. METHODS The total proteins of promastigotes and axenic amastigotes of Leishmania donovani SC6 strain were separated by two-dimensional electrophoresis (2-DE) in a broad pH range (3-10), and the gel was stained with Coomassie blue. The images were analyzed by PDQuest 1.0 software, and the major developmentally regulated proteins were identified by electrospray mass spectrometry. RESULTS Approximately 700 protein spots were revealed in equivalent proteins of the promastigotes and axenic amastigotes separated by 2-DE, among which more than 90% protein spots showed equivalent quantity and distribution, with 6 proteins up-regulated and 3 proteins down-regulated in axenic amastigotes compared with promastigotes. Five of the 6 up-regulated proteins were with known function, respectively ascribed as Rieske iron-sulfur protein precursor, alpha-tubulin, peroxidoxin 1, dihydrolipoamide acetyltransferase precursor, and mannose-1-phosphate guanylyltransferase. Two of the 3 down-regulated proteins were identified as heat shock protein 70 and beta-tubulin. The functions of the developmentally regulated proteins were related to the carbohydrate/energy metabolism, stress response, or formation of cell membrane/cytoskeleton. CONCLUSIONS The findings demonstrate the differences in protein expression profiles between promastigotes and amastigotes.