Abstract: Polydisperse native Pseudomonas flagellar (H) antigens (FAg) and methods of producing them are described, wherein each monomeric component contains certain amino acids, has a certain N-terminal amino acid sequence and a certain molecular weight and is free from pyrogenic substances. The ratio of the individual amino acids in the flagellar antigen of the individual H-serotypes is stated.For producing the polydisperse native Pseudomonas flagellar (H) antigens (FAg) methods are indicated, wherein Pseudomonas aeruginosa bacterial cultures or fractions thereof are treated with a detergent and the flagellar antigens are separated from the cultures. Prior to treatment or in the presence of the detergent, the bacterial culture is subjected to a shearing procedure, i.e. exposed to shearing forces. Thereafter, the flagellar antigens separated from the bacterial mass are isolated by a chromatographic treatment.