Implicit in the optimal isolation of mycoplasmas from the genitourinary tract is the taking of 1) appropriate specimens, along with 2) an understanding and avoidance of the toxicity of certain swabs and antiseptics. Specimens should be 3) transported without undue delay, particularly if quantitative estimations are to be made, and 4) diluted serially in 5) supportive medium or media. The mere fulfillment of a particular medium formulation, however useful the medium is reported to be, is unlikely to lead to success without constant trial and error. The color-change technique, based in the case of ureaplasmas on the metabolism of urea, revolutionized the isolation of these organisms, and is used for other mycoplasmas too. Specific identification may be accomplished by one or more of several techniques, but usually growth inhibition on agar for large-colony-forming mycoplasmas, and metabolism inhibition for ureaplasmas.