Considerable advances have been made in recent years in our understanding of the biochemistry of protein and nucleic acid synthesis and, particularly, the molecular biology of gene expression in eukaryotes. The yeast Saccharomyces cerevisiae, and to a lesser extent Schizosaccharomyces pombe, has had a preeminent role as a focus for these studies, principally because of the facility with which these organisms can be experimentally manipulated biochemically and genetically. This review will be designed to critically examine and integrate recent advances in several vital areas of regulatory control of enzyme synthesis in yeast: structure and organization of DNA, transcriptional regulation, post-transcriptional modification, control of translation, post-translational modification and secretion, and cell-cycle modulation. It will attempt to emphasize and illustrate, where detailed information is available, principal underlying molecular mechanisms, and it will attempt to make relevant comparisons of this material to inferred and demonstrated facets of regulatory control of enzyme and protein synthesis in higher eukaryotes.