Necrotizing soft tissue infection (NSTI) of the upper extremity is characterized by rapid progression, local tissue necrosis, systemic toxicity, and a high mortality rate. The negative consequences of debridement are balanced against preservation of life and limb. The primary objective of this study was to identify predictors of mortality in upper extremity NSTI. Secondary objectives were to identify predictors of amputation, final defect size, length of stay, and readmission within 30 days.