Process for the manufacture of cystine-peptides wherein a cysteine peptide whose mercapto group is substituted by trityl or acylamidomethyl is reacted with Hal-S-CO-OR3 wherein R3 represents an optionally substituted hydrocarbon residue and that the resulting -S-COOR3-protected cysteine peptide is reacted with a cysteine peptide with free mercapto group to yield the corresponding cystine peptide.