Cyclo-beta-tetrapeptide I, a beta-peptidic analog of octreotide, was prepd. from beta-amino acid building blocks synthesized by Arndt-Eistert homologation of appropriately protected alpha-amino acids. The affinity of I for five different human somatostatin receptors was measured using radioligand-binding assays. I had affinity, although the concns. were in the micromolar and not in the nanomolar range as for somatostatin and octreotide. The authors have demonstrated that a small beta-peptide (consisting of only four beta-amino acids) can mimic a natural peptide hormone and display biol. activity and micromolar affinity for human receptors. Thus, beta-peptides can, in principle, be considered as peptidomimetics.