In view of the numerous different yeast strains which are used in studies of mitochondriogenesis, we considered that a comparative study of some of these strains would provide useful information for workers in this field. To this end, we have compared the growth characteristics of several widely used strains and of some randomly selected strains from our culture collection. The yeast were grown on glucose, both aerobically and anaerobically; parameters studied included ethanol metabolism, respiratory quotients, growth rates, and carbon source utilization.The nine strains can be divided into three classes : class 1, Brewers yeast showing very fast fermentation and high ethanol yields together with a pronounced diauxic, aerobic growth curve; class 2, wine yeasts with a slower fermentation rate, lower ethanol yields, and poorer growth under anaerobic conditions; class 3, a miscellaneous collection including auxotrophs, petites, and an obligate aerobic yeast.It is concluded that a large proportion of the work done on mitochondriogenesis has been performed on similar yeast strains but that some caution must be exercised when comparing yeasts from different classes.