Two mycoplasma strains were isolated from dead turkey embryos. Growth properties, biochemical and serological characteristics, and protein profiles indicated that these strains were closely related to Mycoplasma pullorum CKKT (T = type strain). This was confirmed by 16S rRNA sequence analysis, and the phylogenetic position of M. pullorum was established. Pathogenicity studies showed that the two strains, as well as M. pullorum CKKT, induced a statistically significant level of mortality after inoculation into chicken embryos.