Introduction & Objective: Leishmania is a protozoan of the trypanosomatidae family. This protozoan has two stages in its life cycle, promastigote form in sand flies and amastigote form in macrophage of mammalian hosts. The purpose of this study was identification and comparison of proteins of Leishmania amastigote and promastigote stages.

Materials & Methods: The present study is a cross sectional study of two forms of Leishmania major. To culture promastigotes , L.major (MRHO/IR/75/ER) from previously infected Balb/c mice was transferred to modified N.N.N medium with overlay of liquid BHI and then transferred to RPMI-1640 at 26oc ± 1 for mass production. After isolation and growth, promastigotes were transferred to liquid cell culture medium RPMI-1640 with pH 5.5 and incu-bated at 5% CO2 at 37oc for 72 hours until promastigote to amastigote transformation. Elec-trophoresis was performed with SDS-PAGE method to find and compare the molecular weight of the antigens of two stages.

Results: The molecular weights of the bands observed in both forms were as follows: 19, 36, 50, 63, 65, 80, 90, 94, 96, 110- 130 KDa. The proteins in the surface of only promastigote were 22, 28 and 46 KDa and special proteins in the surface of amastigote were 12 and 32 KDa. Conclusion: According to this study Leishmania parasite has stage specific proteins. Various studies have shown that axenic amastigotes and tissue amastigotes are similar in their protein content. Therefore, based on stage specific proteins ,effective drugs and vaccines can be de-signed against leishmaniasis.