Gastric secretory, psychological, and behavioral observations were carried out in 59 experiments in an infant (with a gastric fistula) from the age of 15 to 20 months. Of a number of observed physiological variables, only the total hydrochloric acid secretion rate is considered here. The total hydrochloric acid secretion rate was intimately integrated with the total behavioral activity of the infant. Outgoing affective states, be they libidinal or aggressive, were associated with rising rates of hydrochloric acid secretion. During the Depression-Withdrawal reaction, characterized by facies, muscular flac-cidity, inactivity, and withdrawal from the outside world, progressing into sleep in the more severe instances, there was a marked decrease in or even cessation of hydrochloric acid secretion. The more active transactions with the environment were associated with rising hydrochloric acid secretion rates. Histamine effect on gastric secretion during the Depression-Withdrawal state was slight or absent, whereas during outgoing states histamine was a potent stimulant of hydrochloric acid secretion. This suggests the possibility of an altered organization at the cellular level under these 2 conditions. Results support the psychoanalytic concept that, at this level of development, the establishment of object representations involves an oral, intaking model. Our study lends support to the concept of an oral stage of development as the infant related outgoingly to an experimenter, be it aggressively or libidinally, her gastric glands reacted as if introjection of the cathected object was to take place. It is emphasized that these conclusions apply to this particular infant at this particular stage of development and that generalizations should be made only with caution. The Depression-Withdrawal reaction appeared to be a particular mode of the infant to object loss, the pattern for which was established by her previous de-pressions as observed on 2 admissions to the hospital. The genetic dynamic background of this reaction, which may represent a regression to a pre-oral stage will be considered extensively in a separate communication.