Ultrathin sections of five spore stages of C. ribicola were incubated with wheat germ agglutinin (WGA), which binds to chitin, followed by an ovomucoid-gold complex, which binds to WGA and examined by TEM. Labelling experiments showed the presence of chitin in all five stages of the fungus, although the distribution of chitin varied among spore stages. Competitive inhibition studies with triacetyl chitotriose showed that WGA bound to cell walls of basidiospores much more strongly than other spore types, requiring a 10-fold increase in concentration over that required for the other spore types to achieve complete inhibition.