The Microring YT is a commercial system for identifying clinical yeast isolates. The system uses a series of discs impregnated with inhibitory agents mounted on a ring. The pattern of growth and inhibition produced provides a six digit code which can be compared with a table provided by the manufacturer. The performance of this system was compared with the API 32C in the identification of 606 yeast isolates (355 clinical and 251 environmental strains). The Microring YT system was in 72.6% agreement with the API 32C system. The sensitivity of identification of different species varied from 38% to 100%. The API 32C system has a more extensive database than the Microring YT and is thus more reliable for use, but it is considerably more expensive. It is concluded that although the Microring YT is cheap, easy, and convenient to use, it is inadequate for many common Candida species.