Background: Immune checkpoint inhibitors (ICIs) - anti-PD-1 (nivolumab, pembrolizumab), anti-PD-L1 (atezolizumab, avelumab), anti-CTLA-4 (ipilimumab) - have improved outcomes for several malignancies. ICIs may cause immune-related adverse events (irAEs), often treated with immunosuppression. The incidence of infections arising de novo during ICI therapy or from immunosuppression for irAEs is not well described. Methods: In- and outpatients receiving ICIs were referred for Infectious Diseases consultation between 6/2011-6/2018. Twenty-five were randomly selected for retrospective summarization of the spectrum of infections. Diagnosis of infection was made by the primary oncologist, based upon clinical/radiographic/laboratory data. Results: Solid tumor (24, 96%) and hematologic malignancies (1, 4%) were represented (Table). All 25 had infections. 15 (60%) were male; median age 58 years (29-97). 17 (68%) had irAEs: pneumonitis (10, 40%), thyroiditis (5, 20%), colitis (5, 20%), hepatitis (4, 16%), dermatitis (4, 16%) and myocarditis (1, 4%). 17 (68%) patients developed +1 irAE. 50% with pneumonitis were concurrently treated for pneumonia. Of the 25, 17 (72%) developed de novo infections on ICIs; whereas others were receiving systemic corticosteroids (7, 28%) or infliximab (1, 4%). Initial infections included pneumonia (13, 52%), bacteremia (3, 12%), sinusitis (2, 8%), wound infection (2, 8%), viral infections (HSV, CMV, HCV; 1, 4% each) and 1 (4%) each of empyema, UTI, peritonitis, osteomyelitis, and meningitis. 44% (11) developed a second infection within 60 days of the first. Conclusions: Patients receiving ICIs for cancer developed a myriad of infections, both de novo during ICI therapy, or consequent to immunosuppression for irAEs. Second infections are common, occurring in nearly half the patients. Awareness of this is vital for early diagnosis and appropriate management. Patients with suspected ICI-related infection. (n=25).