The authors describe a procedure for producing the antigen by using a promastigotic suspension of the high-virulent inoculative strain Leishmania major. A Leishmania culture medium was improved to enhance the yield of parasites up to 1-3 billion cells in a flask. The grown culture was washed off with isotonic sodium chloride solution, from the medium residues and concentrated up to 1 billion cells per ml of the cvolume. The cell concentrate contained no rabbit blood additive, as evidenced by the gel double diffusion test. The combinations of destruction via multiple freezing-unfreezing or lyophilization, followed by ultrasound treatment were found to be the best modes of promastigotic disintegration. The antigenic suspension generally displayed 3-5 precipitation lines with hyperimmune rabbit sera and 1-3 precipitation lines with sera from the infected animals. The number of precipitation lines is higher in the suspension from the high-virulent Leishmania strains. Fractions of protective antigens have not been detected so far.