Abstract Nearly one million Americans are hospitalized every year with pneumonia, the most common infection leading to death in the US. Recent data suggest that admission to an intensive care unit (ICU) can reduce mortality for patients with pneumonia, even when they do not require life support. This has prompted calls to increase ICU use for patients with pneumonia, potentially stressing ICU resources. In part to relieve ICU strain, use of ?intermediate care? (IMC) for pneumonia patients in US hospitals has tripled from 8% to 21% of admissions over the last 2 decades. Yet remarkably little is known about IMC beds. IMCs may be a cost-effective way to providing care for pneumonia patients, but may also serve to only increase costs without improving outcomes The goal of this proposal is to characterize the dominant organizational phenotypes, care practices, and contextual factors and strategies associated with effective IMC implementation for individuals with pneumonia in a large and representative sample of US hospitals. We propose using a mixed-methods approach that combines econometric analysis of claims data, surveys, and site visits to address the following aims: Aim 1. We will empirically evaluate and classify the phenotypes of IMC use by linking data from hospitalized patients with pneumonia receiving care in IMCs with surveys of leaders within the same hospitals that capture the environment, staffing, and organizational features of those IMCs. Aim 2. We will determine the effect of IMC phenotype on outcomes of patients with pneumonia. The analyses in this aim will also be instrumental in defining a group of high-performing hospitals with the dominant phenotype of IMC that deliver effective IMC to patients with pneumonia. Aim 3. We will define optimal practices at sites with the best pneumonia outcomes associated with IMC by performing site visits to the top-, mid-, and low-performing hospitals with the dominant phenotype of IMC. Through site tours, interviews of key informants, observations, and document collection, we will collect data on each institution's resources, review intermediate care policies and protocols to identify the contextual factors and strategies associated with effective IMC delivery. This project will fill a large knowledge gap in our understanding of provision of hospital care for pneumonia patients. STEP-IN will provide the first comprehensive picture of IMC for pneumonia in the US, identifying models of care associated with reduced deaths from pneumonia. Using this foundation, we will identify also candidate best practices to improve care for pneumonia in IMC, and define the organizational contexts across which to disseminate such practices. The proposed work of STEP IN will lead directly in STEP IN 2 to definitive implementation trials of such best practices, and is organized to expedite that move to rapid translation.