The serum gastrin response to three different amounts of a same meal was studied in 8 normal subjects. The peak gastrin response was similar for the three meals, but the integrated gastrin response was larger with the largest meals. Comparison of the response to the two largest meals indicates that in a given subject the gastrin response is similar when tested on different occasions. A good correlation was found between individual fasting concentrations of gastrin and peak gastrin levels after feeding but not between basal gastrin and integrated gastrin response. This could indicate that in normal subjects the first two parameters are primarily related to the same control mechanisms (possibly the G cell mass), while the integrated gastrin response reflects the effectiveness of the feedback mechanisms controlling gastrin release.