NB41A3 cells were used to investigate the membrane binding and incorporation of a synthetic beta-amyloid peptide, beta-1-40. After 18 hours cells exposed to the 1-mu-M peptide showed decreased survival. No specific binding of the radiolabeled peptide could be detected after 1 hour incubation with the cells, however specific binding was detected after a 20 hour incubation period. After washing the cells, the peptide was detected inside the cells. Amyloid may exert its biological activity by a complex mechanism including specific surface binding following by internalization into the cell.