Despite efforts to decrease lengths of acute psychiatric hospital stays, some geriatric inpatients continue to have extended stays. This research examined factors related to length of stay (LOS), including legal and administrative factors not traditionally included in prior studies. The charts of 384 patients, representing all 464 discharges from an inpatient geropsychiatric unit over a one-year period, were evaluated retrospectively and analyzed using logistic regression and logarithmic transformation. The LOS of over 12% of the inpatients was 26 days or more (average LOS 14.1). Factors significantly associated with longer LOS were: receiving electroconvulsive therapy (ECT), higher Brief Psychiatric Rating Scale (BPRS) positive symptoms scores, falling, pharmacology complications, multiple prior psychiatric hospitalizations, requiring court proceedings to continue hospitalization or medicate against will, consultation delays and not performing ECT on weekends. Neither demographics nor diagnoses alone had influence on length of stay. Incorporation of LOS predictors into Medicare Inpatient Prospective Payment System (IPPS) would more accurately account for the complexity in the cost of caring for geropsychiatry patients.