Abstract: A process for synthesizing peptides or peptide derivatives is disclosed. The process involves using aminoacyl-tRNA synthetase as a condensing agent when synthesizing peptides or peptide derivatives from amino acids. According to the process, peptides or peptide derivatives which are useful as various hormones such as bradykinin having antihypertensive activity or somatostatin having an internal or external secretion controlling function and other biologically active substances such as antibiotic peptides or seasoning peptides can be produced at a moderate price without using protective groups.