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BACKGROUND AND AIMS The utility of high-resolution anorectal manometry (HR-ARM) for diagnosing defecatory disorders (DDs) is unclear because healthy people may have features of dyssynergia. We aimed to identify objective diagnostic criteria for DD and to ascertain the utility of HR-ARM for diagnosing DD. METHODS Constipated patients were assessed with HR-ARM and rectal balloon expulsion test (BET), and a subset underwent defecography. Normal values were established by assessing 184 sex-matched healthy persons. Logistic regression models evaluated the association of abnormal HR-ARM findings with prolonged BET and reduced rectal evacuation (determined by defecography). RESULTS Four hundred seventy-four constipated persons (420 women) underwent HR-ARM and BET; 158 underwent defecography. BET was prolonged, suggesting a DD, for 152 patients (32%). Rectal evacuation was lower for patients with prolonged vs normal BET. A lower rectoanal gradient during evacuation, reduced anal squeeze increment, and reduced rectal sensation were independently associated with abnormal BETs; the rectoanal gradient was 36% sensitive and 85% specific for prolonged BET. A lower rectoanal gradient and prolonged BET were independently associated with incomplete evacuation. Among constipated patients, the probability of reduced rectal evacuation was 14% when gradient and BET were both normal, 45% when either was abnormal, and 75% when both variables were abnormal. CONCLUSIONS HR-ARM, BET, and defecography findings were concordant for constipated patients, and reduced rectoanal gradient was the best HR-ARM predictor of prolonged BET or reduced rectal evacuation. Prolonged BET, reduced gradient, and incomplete evacuation each independently supported a diagnosis of DD in constipated patients. We propose the terms probable DD for patients with an isolated abnormal gradient or BET and definite DD for patients with abnormal results from both tests.