Abstract: The invention consists of peptides which inhibit the secretion of neurotransmitters from synaptic vesicles. The peptides of the invention are believed to mimic the activity of neurotoxins produced by Clostridium botulinum and tetani (including botulinum serotypes A, B, C, D, E, F and G). Structurally, the peptides are comprised of amino acid fragments from the substrate binding domains selected from three proteins which bind to form a receptor for docking of synaptic vesicles to the plasma membranes of neuronal cells; i.e., SNAP-25, VAMP-2 and syntaxin. Certain of the inventive peptides exhibit strong inhibitory activity; e.g., 50% or greater decline in neurotransmitter release is obtained at even nanomolar concentrations. The peptides are suited for use as substitutes for Clostridium neurotoxins in clinical applications and in compounds for targeted delivery of drugs into neural cells.