OBJECTIVES:  Despite several studies have proved that procalcitonin-guided antibiotic use reduces antibiotic consumption, whether to comply procalcitonin protocol in clinical practice remains controversial. The aim of study was to estimate the cost-effectiveness of procalcitonin to guide antibiotics usage compared with usual care in patients with community acquired pneumonia (CAP). METHODS:  The study was conducted from a third-party payer perspective. A decision analysis using data obtained from published observational studies, clinical trials, and the claims data from National Health Insurance Research (NHI) Database of Taiwan between 2002 and 2011. We considered 60% overrule recommendation in a decision tree model. We performed probabilistic sensitivity analyses, acceptability curves and estimated quality-adjusted life-years (QALYs). RESULTS:  Two million individuals sampled randomly from the 24 million subjects enrolled in the NHI were used to obtain CAP inpatient subjects. Among 3,884 patients, the average length of stay for patients hospitalized with CAP was 13 days. There was a 1.51 day reduction for procalcitonin protocol group in the mean length of stay. The average total medical cost was $2676.3 in the usual care group and $2569.1 in the procalcitonin group. The procalcitonin-based algorithm was associated with a reduction in costs of $107.2 and an increase in QALY of 0.00083 under 60% overrule procalcitonin protocol, generating a negative incremental cost-effectiveness ratio of [$129158.2]. The sensitivity analysis showed that high protocol non-adherence ranged from 60-90% still resulted in cost-effective outcomes. Sensitivity analysis showed that procalcitonin-guided antibiotic use remains acceptable under a broad range of assumptions. CONCLUSIONS: This is the first study using a claims database to compare procalcitonin protocol and usual care among CAP patients in Taiwan. We confirmed cost-effectiveness of procalcitonin-guided antibiotic use even though the physician adherence rate was poor. Policy makers may learn from the study and take actions to improve adherence rates of procalcitonin-based antibiotics stewardship.