Unnecessary antibiotic use significantly contributes to increasing bacterial resistance, medical costs and the risk of drug-related adverse events. The blood marker procalcitonin increases in bacterial infections and decreases when patients recover from the infection. Hence, procalcitonin may be used to support clinical decision making for the initiation and discontinuation of antibiotic therapy in patients with a clinical suspicion of infection. Randomised controlled trials have demonstrated that such a strategy works, particularly in patients with an infection of the respiratory tract. However, most of these individual studies did not include enough patients to allow for a conclusive assessment about safety (low statistical power). Thus, the risk for mortality and severe complications associated with procalcitonin-guided decision making remained unclear. This systematic review included individual patient data from 14 randomised controlled trials with a total of 4211 participants. When looking at these combined data, we found no increased risk for all-cause mortality or treatment failure when procalcitonin was used to guide initiation and duration of antibiotic treatment in participants with acute respiratory infections compared to control participants. However, we found a consistent reduction of antibiotic use, mainly due to lower prescription rates in primary care and lower duration of antibiotic courses in emergency department and intensive care unit patients. This analysis is limited to adult patients with respiratory infections excluding patients who were immuno-compromised (i.e. HIV positive, those receiving immuno-suppressive therapies or chemotherapy). Most trials were conducted in Europe and China and similar studies in other countries including the United States are warranted.