Background: Procalcitonin (PCT) is a biomarker that has been showing promising results in differentiating bacterial infections from viral infections. Due to the increasing global problem concerning antibiotic resistance, there is a need to reduce antibiotic consumption. The rate of antibiotic prescription is especially high in respiratory tract infections. There has been done a lot of research on PCT and respiratory tract infections. Some Norwegian hospitals have already implemented the use of PCT. Before implementing PCT in Ullevål, a mini-method evaluation was done. Methods: In this paper we look at the studies in the mini-method evaluation concerning respiratory tract infections. We have focused especially on community acquired pneumonia (CAP) and exacerbations of COPD. Results: The largest meta-analysis on the topic shows that PCT guidance significantly reduces the total antibiotic exposure for patients with respiratory tract infections. The duration of the antibiotic treatment is reduced from ten days to seven days (median, P<0.001) and the antibiotic initiation is reduced from 84 percent to 64 percent (P<0.001). The most significant reduction is found in the group with CAP. Conclusion: PCT-guided antibiotic treatment for respiratory tract infections can significantly reduce the consumption of antibiotics, without increasing mortality or any other adverse outcomes. PCT-guided antibiotic treatment is a good tool for reducing the use of antibiotics for patients hospitalized with CAP. PCT-guidance also shows a good potential for reducing antibiotic prescription for patients hospitalized with exacerbation of COPD.