The effects of temperature on the kinetics and efficiency of secretion of cloned invertase were investigated in a recombinant yeast system. This system consisted of the baker’s yeast Saccharomyces cerevisiae (SEY2102) transformed with the 2 mu-based plasmid pBR58 which contains the entire SUC2 gene including the promoter, signal sequence, and structural gene. The recombinant yeast produces the naturally secreted yeast enzyme invertase, In transition experiments done at temperatures ranging from 25 degrees to 45 degrees C, the maximum invertase level and secretion rate exhibited maxima of 5.5 U/mL . OD and 4.6 U/mL . OD per hour, respectively, at 35 degrees C. Experiments involving the use of cycloheximide showed that it took approximately 15 min for secreted invertase to move through the secretion pathway, which held 0.4 U/mL . OD of specific activity.