Glycine (250 ml 0.3 M glycine) was administered orally to 19 nonobese normal subjects and 12 subjects with partial gastrectomy. In the normal subjects, a clear and significant increase of serum human growth hormone (hGH) level was observed (p less than 0.001), whereas serum immunoreactive insulin (IRI), prolactin (PRL) and blood sugar (BS) levels were not affected after the drug administration. A more pronounced and significant increase of hGH value in serum was found in the subjects with gastrectomy than in the normal controls (p less than 0.001). Thus we administered the drug intraduodenally in normal subjects. The similar rise of hGH to that of the gastrectomied group was obtained in normals by this administration. The facts demonstrated that glycine is one of the stimulatory agents inducing the pituitary gland to secrete hGH. In addition, in nonobese diabetics, no significant increase of serum hGH level, even after the intraduodenal administration of glycine, was observed in the present study.