Cultures (43) of apiculate yeasts were examined for the coenzyme Q (Co-Q) system, which belong to the genera Nadsonia, [N. elongata, N. fluvescens] Saccharomycodes [S. ludwigii], Wickerhamia and Hanseniaspora [H. osmophila, H. vineae, H. uvarum, H. valbyensis, H. guilliermondii] and its imperfect counterpart of Kloeckera [K. africana, K. apiculata, K. corticis, K. magna, K. javanica, K. jensenii, K. antillarum, K. lafarii, K. japonica]. All species of these genera had the Q-6 system except for the only Wickerhamia sp. (Q-9) [W. fluorescens]. Results are discussed in connection with other criteria such as PMR spectra of cell wall polysaccharides, DNA base composition and serological characteristics. This method is described as a criterion for grouping yeasts and yeast-like organisms.