Objectives To study the changes of gastrointestinal hormones in chronic constipation. Methods 17 outpatient chronic constipation patients, and 10 normal persons were respectively chosen as observation group and control group. Fasting blood samples were taken in all patients. The serum levels of somatostatin (SS) and substance P (SP) were tested using RIA method.Results The serum level of SS and SP in observation group were (120.57?27.84)pg/ml and (7.68?2.5)pg/ml respectively, significantly higher than that in control group (P