Trichosporin (TS)-B-VIa, a peptide consisting of 19 amino acid residues and an amino alcohol, causes Ca²⁺-dependent secretion of catecholamines from bovine adrenal chromaffin cells. The TS-B-VIa-induced secretion was greater under alkaline conditions and at a temperature of 37°C compared with that at 21° or 30°C. It was not observed when the peptide was eliminated from the incubation medium. These results strongly suggest that the stimulatory effect of TS-B-VIa on the secretion is reversible and dependent on the temperature and pH of the incubation medium.