Serum growth hormone, glucose, and insulin were studied every half hour during a twenty-four-hour period of "daily life" in four groups of subjects: nonobese normal subjects, obese normal subjects, nonobese maturity-onset diabetics, and obese maturity-onset diabetics. It was found that (1) serum growth horomone was uniformly low without meal- and sleep-related peaks in obese normals and diabetics. The twenty-four-hour serum growth hormone level was significantly higher in nonobese subjects than in obese subjects, in both diabetics and normals; (2) the twenty-four-hour serum growth hormone level was more fluctuating and significantly higher in nonobese diabetics than in nonobese normals; (3) there was no difference in the twenty-four-hour serum growth hormone level between obese diabetics and obese normals.