Restriction endonuclease analysis (REA) and immunoblotting were used to compare field strains of Mycoplasma mycoides subsp. mycoides biotype Small Colony from different parts of Europe and Africa. Of the 27 strains tested by REA, the European ones (n = 15), except 3 from the Iberian peninsula, differed strikingly from the African ones (n = 10). Vaccinal strains T 1 - SR and KH 3 J had a unique REA pattern.Polyclonal immunoblot profiles of 46 strains appeared fairly similar. However most of the Italian strains (22 out of 24) shared a characteristics, in the 100 kDa area, unlike that of the other European strains. Immunoprofiles of the reference strain PG1 and vaccinal strain T 1 -SR were different from the others.These results allowed the determination of possible links between different geographic region of enzootic contagious bovine pleuropneumonia.