Several aspects of the role of acetate metabolism in the sporulation of Saccaromyces carlsbergensis were investigated. Experiments in which the development of the respiratory system was either stimulated by growth on sugars to which the cells have to adapt, or inhibited by chloramphenicol suggested a correlation between respiratory development and sporulation. In cells in which the respiratory system has been repressed during growth, mitobhondrial protein synthesis and derepression are prerequisites for sporulation. When derepression is complete, sporulation no longer depends on mitochondrial protein synthesis. Incorporation experiments with acetate showed that this compound is an important source of intermediates for biosynthetic processes that occur during sporulation. Its incorporation into macromolecular fractions is tightly coupled to sporutlation.