Hospital discharge planning is the process of assessing the needs of hospitalized patients for post-acute care and developing a coordinated plan to provide the care needed. It is an important component of both the financial viability of the hospital and of the overall quality of care provided to the patient across health care settings, and has historically been an important part of social work practice. This research, based on a random sample survey of U.S. non-federal acute medical/surgical hospitals (N = 378 hospitals), suggests those variables that may be most important in shaping the effectiveness of the hospital discharge planning program. A multivariate analysis framework is used to identify those variables that have the strongest independent effect on effectiveness, and to assess the relative strength of each. Power (including discharge planner influence and physician and hospital administrator support) and role clarity emerge as the most important predictors of perceived effectiveness. The model of discharge planning used and characteristics of the hospital (such as size or urban-rural location) are not significant independent predictors. The single most important factor is cooperation and support from the physician staff of the hospital. This research suggests that organizational factors, rather than the use of a particular "system" of discharge planning, may be most important in discharge planning effectiveness.