OBJECTIVES: To investigate the association of the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO) core performance measures, practice guidelines and other factors with hospital length of stay (LOS) and mortality in patients with community-acquired pneumonia (CAP), heart failure (HF) or sedated intensive care unit (ICU) patients. METHODS: Data included 2238 patients with CAP, 622 patients admitted to the ICU and 1340 patients with HF, from 88 hospitals during a 3-month period. Data included patient demographic, hospital characteristics and outcome measures. Univariate and multivariate analyses such as ordinary least square (OLS) and logistic regression were performed. RESULTS: Based on the results from OLS regression analysis, older age is significantly associated with longer LOS (p<0.0001) for all conditions. Also, patient admission to hospitals with a care plan (p<0.0120) and the number of patient co-existing illnesses (p<0.0016) were significantly related to an increase in LOS. Patients receiving care according to practice guidelines have a significantly shorter LOS. Logistic regression results show that older age (odds ratio, OR=1.029, p<0.0001) and male gender (OR=0.701, p<0.0036) were significantly associated with higher mortality. Compliance with practice guidelines had a significant impact on decreasing mortality regardless of conditions. CONCLUSIONS: Compliance with practice guidelines may reduce LOS and mortality, which suggests improved patient outcomes and decreased healthcare costs.