The spectrum of pneumonia patients ranges from only slightly compromised patients to patients who require life-sustaining measures. Admission decision support algorithms usually are not required for patients at either end of the spectrum. For patients presenting with intermediate severity of illness, decision support algorithms have shown that they can support clinicians in the admission decision and complement the clinicians' experience and clinical judgment with an objective tool. Clinical information systems may help overcome the existing obstacles to successful implementation. Successful guideline implementation in a clinical setting includes strategies that target not only the disease, but also include other forces that significantly influence the admission decision. Shared decision making and better managing of patients' expectations about treatment and prognosis need to be incorporated in the overall admission decision. The availability of improved outpatient management, such as outpatient intravenous antibiotic treatment and home health care, and a change in physicians' perspectives and patients' expectations may help to increase the proportion of outpatient management without compromising the quality of care. Decision support tools for pneumonia are available and show promising results. Further studies are needed, however, that show the successful dissemination and clinical implementation during routine patient care. Studies are needed that assess the impact of guidelines and prediction rules on patient outcomes. As the example of the PSI shows, the development, implementation, and dissemination of admission decision support systems is not a revolutionary, but a stepwise, evolutionary process that requires many years of research.