The relationship between patient-staff ratio and the prevalence of patient incidents, such as assaults, fighting, suicides, falls, and abuse of patients by staff, was examined at an urban inpatient psychiatric center. Stepwise logistic regression was used to analyze 5,375 shifts in 14 high-incident wards representing five types of inpatient services; sample periods from three different years were examined. At least one incident occurred during 411 shifts (7.6 percent). More incidents occurred on the day shift and on two specific wards, confirming previous findings of a relationship between incidents and time of day as well as patient characteristics and milieu. However, no relationship between patient-staff ratio and the occurrence of incidents was found. This finding suggests that small increases in the number of ward staff may not reduce the number of patient incidents.