Psychiatric consultation timing results from the interaction of multiple systems. This study examines the key clinical and systems variables and the effect of consultation timing on subsequent length of hospital stay. One hundred and forty-five consecutive psychiatric consultations at a New York City teaching hospital were assessed by demographic criteria, medical and psychiatric diagnoses, reasons for consultation, and the timing of the consultation with respect to the academic year. Twenty-five percent of the consultations occurred within the first 48 hours after admission and 32% occurred between Days 2 and 5. Consultations for schizophrenia patients were called earlier (P < 0.02) than those for patients with other diagnoses, and those for patients with the acquired immunodeficiency syndrome were called later (P < 0.04). Earlier consultations were associated with a shorter time to discharge (P < 0.002).