Yeast strain is an important factor in determining character of a finished beer. Strain differentiation and evaluation of brewery yeasts have not received the attention they warrant despite their importance in strain selection and maintenance. A guide to the biochemical methods used by the author in evaluation of yeast for brewing is provided, with examples from a number of strains of S. Carlsbergensis and S. Cerevisiae. Particular attention is paid to the physiological condition of the yeast at the time of testing. Of special importance in evaluating a yeast strain is the kinetics of yeast growth and the rate of adaptation to ferment maltose or maltotriose. Other .factors such as flocculation, adsorp and production of volatile substances have also been investigated.