Background: Only few data are available on the efficacy of tigecycline in critically ill patients. Methods: This prospective, multicenter, non-interventional study investigated the efficacy and safety of tigecycline in hospitalized, severely ill patients with complicated intra-abdominal infections (cIAI) and/or complicated skin and soft tissue infections (cSSTI). Documentation included diagnosis, clinical findings, Acute Physiology and Chronic Health Evaluation II score, laboratory assessments, surgery, clinical outcomes, and adverse events. Results: Six hundred and fifty-six patients (mean Acute Physiology and Chronic Health Evaluation II score 19.1) with cIAI (41%), cSSTI (16%), multiple infection sites (13%) and/or other severe infections (31%) received tigecycline â 51% as monotherapy â due to failure of previous antibiotics (55%) or since resistant pathogens were suspected or proven (45%); clinical cure/improvement rates were 75, 82, 76 and 67% for cIAI, cSSTI, other severe infections and multiple infection sites, respectively. Drug-related adverse events occurred in 6.7% of patients. Conclusions: The efficacy and safety of tigecycline was demonstrated in a population of severely ill patients with complicated infections.