The polymerase chain reaction was used for rapid detection and differentiation between different strains of Mycoplasmagallisepticum. Two oligonucleotide primers of 22 and 23 base pair in length were constructed. The PCR amplification products were visualized by ethidium bromide and ultraviolet exposure. The results were as follows: 1. A positive single PCR product 960 bp in size was detected for Mycoplasma gallisepticum (56 strains). 2. Other strains of mycoplasma (oral, arginini, salivarium and pneumonia) showed no band at 960 bp molecular weight. This technique provides a simple and extremely sensitive method of identifing isolates of M. gallisepticum and other Mycoplasmas.