Abstract: The GDP-mannose transporter gene VRG4 has been identified from a number of yeasts including Saccharomyces cerevisiae. The vrg4-2 allele of the GDP-mannose transporter of S. cerevisiae has been primarily characterized as having general phenotypes affecting glycosylation. In this study, vrg4-2 was characterized, specifically with regard to defects in cell wall biosynthesis. The cell wall in vrg4-2 mutants was found to be profoundly compromised, as measured by the spheroplast lysis assay. These mutant cells exhibited increased sensitivity to Congo red which is believed to interfere with chitin-glucan assembly in the cell wall. An increased level of cell wall fluorescence was also observed when the cells were incubated with Calcofluor white suggesting an increased level of chitin in the wall. Despite these apparent major alterations in the cell wall, the vrg4-2 mutants exhibited near normal growth relative to the wild-type. All together, these results suggest that vrg4-2 mutation affects the cell wall structure, but less so in general cellular metabolism.