Eleven fluorescein isothiocyanate-conjugated (FITC) lectins, each with distinct carbohydrate-binding properties, were used to assess cell surface glycoconjugates of embryonic and early postnatal cerebellar cells in vitro. Fluorescence staining of embryonic day 13 (E13) cerebellar cells with FITC Ricinus communis agglutinin diminished markedly between 24 and 72 hr in vitro. No staining of postnatal day 0 (P0) or postnatal day 7 (P7) cells was observed with FITC Ricinus communis agglutinin. A similar, but less pronounced decrease in FITC concanavalin A, FITC Lens culinaris, and FITC wheat germ agglutinin was observed between embryonic day 13 and birth. No specific staining of E13, P0, or P7 cultures was observed with FITC peanut agglutinin, FITC Dolichos bifloris agglutinin, FITC soybean agglutinin, FITC Wistaria floribundis agglutinin, FITC Phaseolus vulgaris agglutinin, FITC Limulus polyphemus agglutinin, or FITC Ulex europaeusI agglutinin. Similar results were obtained with 125I-lectin binding assays. Ricinus communis 125-I-agglutinin binding decreased dramatically between embryonic day 13 and birth. Less pronounced decreases were observed in 125I-concanavalin A and wheat germ 125I-agglutinin binding. Very low levels of soybean 125I-agglutinin or Ulex europaeusI 125I-agglutinin were bound by either embryonic or early postnatal cerebellar cells in vitro.