Results obtained from 186 patients hospitalized with pneumonia undergoing treatment with an ACE inhibitor demonstrated that a 30-day mortality rate (9.2%) was associated with the use of lipophilic ACE inhibitors (quinapril, fosinopril, ramipril), but not of hydrophilic ACE inhibitors (lisinopril, captopril, enalapril). Here, ACE is linked to susceptibility to pneumonia measurement.