A solid, urea-containing medium buffered to pH 6.5 with a suitable mixture of KH2P04 and Na2HP04 produced enlarged T-mycoplasma colonies containing a white precipitate. This was absent from M. horninis colonies. The medium can be used for the isolation and identification of T-mycoplasmas. We would like to thank Mr A. E. Pink for assistance with the analyses and Mr E. J. Kentish for the photography.