It is well documented that small basic peptides with lipophilic counterparts induce non-cytolytic histamine release particularly from rat peritoneal mast cells, and to a lesser extent from human leukocytes. Since pro-albumin hexapeptide with its lipophilic core also exhibits a high percentage of basic amino acid residues, it was thought valid to investigate its potential histamine releasing activity using the above-mentioned cell systems. Results show that the peptide failed in both cell types to induce histamine release, or to inhibit IgE mediated or anaphylatoxin induced histamine release up to concentrations of 10(-4) M.