Background: Anti-programmed cell death receptor-1 (PD-1) and anti-CTLA4 antibodies represent an effective anti-cancer. Ipilimumab and nivolumab can induce immune-related adverse events (IrAEs). These IrAEs affect skin, gastrointestinal tract, liver, endocrine system and other organ systems. Life-threatening and fatal irAEs have been reported; adequate diagnosis and management are essential. Methods: A retrospective review of data from 40 patients (pts) records were used to describe the IrAE’s associated with 15 pts treated with ipilimumab and 25 pts treated with nivolumab. Results: A total of 40 pts (25 males and 15 females) were included in the analysis. The median age was 63 years (range 30 - 85 years). The performance status (PS) ranged from 0 to 2, with a median PS of 1. In total, 3 pts with metastatic melanoma, 18 with non small cell lung cancer (NSCLC), 2 with renal cell carcinoma and 2 with Hodgkin’s disease were treated with nivolumab and 15 with metastatic melanoma received ipilimumab. A total of 167 cycles of nivolumab (median = 4, range 1-16) and 60 cycles of ipilimumab (median = 4 cycles, range 1-4 cycles) were administered. Seven IrAEs are described in 19 pts treated with ipilimumab. These include endocrinopathy in 3 pts (hypophysitis in pt and hyphothyroidsm in 2 pts), colitis in 3 pts (1 required infliximab) and hepatitis in 1 pt. Among the pts treated with nivolumab 7 IrAEs were documented. These included pneumonitis in 2 pts, skin rash in 3 pts, mild diarrhea in 1 pt and mild uveitis in 1 pt. Additionally, 3 chest infections were documented including a case of pulmonary tuberculosis in a pt with NSCLC. Conclusions: Anti-PD1 and anti-CTLA4 antibodies can induce a plethora of irAEs. Colitis was more common with ipilimumab while pneumonitis more common with nivolumab. The knowledge of IrAE’s will allow prompt diagnosis and improve the management resulting in decreased morbidity.