The major obstacle to the use of neuropeptides in the pharmacotherapy of brain diseases is their delivery to the CNS. This report presents a novel method for the in vitro molecular packaging of peptides that allows their delivery across the blood-brain barrier (BBB) following systemic administration. The molecular packaging is intended both to disguise the peptide nature of the molecule, thus protecting it from a plethora of vascular and BBB peptidases, and to "lock in" the peptide precursor. The delivered peptide-precursor complex is designed to undergo sequential metabolism, resulting in the release of the active peptide. The proposed method for the CNS delivery of neuroactive peptides results in the brain delivery of the intact peptide sequence, and the delivered peptides exhibit appropriate pharmacological activity. This method may be applicable to delivery of a variety of peptides to the CNS and hence opens the possibility of peptide therapy for CNS diseases that are particularly common in the elderly.