An improved lectin assay was recently developed to determine the density of lectin sites present on the surface of a haploid strain 1209 of Saccharomyces cerevisiae exhibiting the Flo1 phenotype. The assay is based on the use of FITC-avidin which contains a mannose side chain which functions as a binding site to the cell wall lectins termed zymolectins. An examination of the effect of culture time on the zymolectin density indicated no significant effect (P > 0.05) confirming other findings that Flo1 acts in a constitutive manner. Zymolectin densities for this strain averaged 5.4 x 10(6) sites cell-1.