We have examined the pattern of synthesis of the glycoprotein form of invertase and of the smaller carbohydratefree from in synchronous culture to obtain further infromation concerning their biosynthetic relationship. Saccharomyces mutant 1710 was chosen since its invertase production is almost completely derepressed during growth in 0.1 M mannose medium. The large enzyme, unlike the small form, binds to concanavalin A-Sepharose, and on this basis the two types can conveniently be separated for analysis. Large invertase was produced throughout the cell cycle. Synthesis of the small invertase was periodic; the single burst occurred at or close to the budding stage. Tunicamycin, which inhibits the sypthesis of external glycoproteins, halted formation of the large enzyme but not of the small form, and there was no accumulation of invertase activity with the properties of the small enzyme. Hence, it is unlikely that the small form is a precursor of the large one. Despite marked differences in their amino acid compositions, the two enzymes have many similarities. They are probably, in part, the products of the same gene(s), and the differences between them may largely reflect differences in post-translational processing.