The paper presents selected aspects of the transport and metabolism of thiamine in the cells of Saccharomyces cerevisiae, emphasizing the action in these processes of proteins unique to this microorganism. One of them (THI6 gene product) is combined in one molecule two activities needed at subsequent stages of the synthesis of thiamin. Another enzyme, acid phosphatase present in the periplasmic space (pHo3 gene product) has additionally a separate thiamine binding activity. It plays a likely function of thiamine phosphate dephosphorylation downloaded from the outside.