We have recently shown that a variety of proteins, including albumin and immunoglobulins conjugated to colloidal gold, strongly binds to certain basic peptide sequences, and neurohormonal peptides. Silver proteinate, used in the classical Bodian's neurohistological procedure, is now shown to bind to the same peptide sequences in cytochemical model systems. In tissue, gastrin cells and glucagon cells have been reported to show strong unspecific immunocytochemical staining and these cell types also stain in the Bodian's procedure. These results suggest that certain types of unspecific immunocytochemical staining and the Bodian's silver staining method may depend upon a common mechanism, involving binding of labelled or aggregated protein to basic and hydrophobic sequences in tissue.