Four carbohydrate derivatives of poly-D-lysine have been synthesized and assayed as substrates for the tissue culture of embryonic mouse cerebellar cells. On poly-beta-(D-glucopyranosyl)-poly-D-lysine and on poly-beta-(N-acetyl-D-glucosaminyl)-poly-D-lysine, dissociated cerebellar cells formed a monolayer. On poly-beta-(D-galactopyranosyl)-poly-D-lysine, cellular aggregates were formed and cables of processes were extended between the aggregates. On poly-beta-(L-fucosyl)-poly-D-lysine, cerebellar cells failed to attach and died within 24 h. On poly-(N-acetyl)-poly-D-lysine, cell attachment was identical to that on poly-D-lysine. At low concentrations of underivatized poly-D-lysine (0.5-2.0 microgram/ml) dissociated embryonic cerebellar cells formed cellular aggregates, whereas at higher concentrations of poly-D-lysine monolayering was extensive.