A new detection test for the mycoplasmas causing contagious agalactia, Mycoplasma agalactiae, M. capricolum subsp. capricolum and M. mycoides subsp. mycoides L. C., was developed. It was based on two polymerase chain reaction assays: the Ma-PCR for the detection of M. agalactiae and the MYC-PCR for the 'mycoides cluster' thus including M. capricolum subsp. capricolum and M. mycoides subsp. mycoides L. C. An M. agalactiae strain was identified by a 933-bp Ma-PCR product and no amplification with the MYC-PCR. In contrast, a 460-bp MYC-PCR product and a negative or a 350-bp Ma-PCR product characterized a 'mycoides cluster' strain. M. capricolum subsp. capricolum and M. mycoides subsp. mycoides L. C. were identified by their species-specific AseI pattern of the 460-bp MYC-PCR product.