Three analogs of the amino terminal nonadecopeptide of adrenocorticotropin which incorporate cystine cystine bridges between positions (5, 10), (3, 10), or (2, 10) have been synthesized. All of the peptide analogs showed reduced biological activity; however, the peptide with the 5, 10 cystine bridge was shown to possess significantly higher lipolytic activity in rat fat cells than the peptides with a 3, 10 or 2, 10 cystine bridge.