Five commercial antifungal susceptibility testing systems were studied for repeatability and reproducibility as well as concordance of results with the MICs for ten reference strains belonging to six different species. Repeatability was determined by testing each strain in triplicate on the same day, and reproducibility by repeating this triple determination on three different days. On the basis of 630 yeast-antifungal agent results for Mycototal and Mycostandard, 540 for Candifast, and 450 for ATB Fungus and Diff Test, repeatability was consistently equal to or greater than 95%. Reproducibility was 80.07% for Candifast and greater than 95% for the other systems. The concordance with the reference MICs was 51.65% for Candifast, 75.33% for ATB Fungus, 80.89% for Diff Test, 90.16% for Mycostandard and 90.32% for Mycototal. Although the performance of Diff Test and ATB Fungus was satisfactory, Mycototal and Mycostandard gave notably better results with imidazoles. Mycostandard, which is easier to use and includes tests for fluconazole and itraconazole, would seem to be potentially the most useful antifungal susceptibility test available at present.