We studied plasma gastrin levels in 12 healthy men before and after 4, 8 and 10 days of total food deprivation. The gastrin levels during the starvation period were significantly lower than the preexposure values. No such changes were observed in 6 other men, serving as controls, who were allowed to eat ad libitum during the experiment. Blood glucose levels and urinary output of catecholamines were measured concurrently. A pronounced hypoglycemia and a doubting of the urinary output of adrenaline were observed during the fasting period. Thus, depression of plasma gastrin concentrations occurs during starvation despite the presence of some potent gastrin-releasing factors, such as hypoglycemia and increased release of adrenaline. It is suggested that these depressions could be due to the absence of another potent stimulator of gastrin release, namely food in the stomach, or to neurogenic inhibition of gastrin release secondary to a stress-induced elevation of the sympathetic tone.