Forty strains which were stocked as Pichia membranifaciens sensu Kurtzman and 9 strains stocked as Candida valida, anamorphs of P. membranifaciens, in the Institute for Fermentation, Osaka (IFO) were reclassified based on the data of base composition of nuclear DNA, DNA/DNA hybridization, coenzyme Q system, electrophoretic karyotype, and base sequence of 18S rDNA. P. membranifaciens complex was assigned into 3 groups: (I) P. membranifaciens group, including 25 strains with high DNA homologies to the type strain of P. membranifaciens (72-98%); (II) P. manshurica group, including 18 strains with high DNA homology of 79-95% to the type strain of P. manshurica; and a group including the remaining 6 strains, which had low DNA homology to the above two species. GC content was 42.9-45.3 mol% for the P. membranifaciens group, 40.0-42.0 mol% for the P. manshurica group, and 27.2-44.7 mol% for the remaining group. All three groups had ubiquinone Co Q-7. Of the 6 anomalous strains, IFO 0162 was identified as Pichia deserticola, and IFO 0839 and IFO 0840 were identified as Issatchenkia occidentalis; but IFO 0842, IFO 0843, and IFO 1788 were thought to be unknown strains.