PURPOSE: Chest pain, abdominal pain, and headache are common symptoms associated with critical illness. Here, we aimed to evaluate predictors associated with critical illness in young males of the Republic of Korea Army. METHODS: We retrospectively reviewed previously healthy young males with chest pain, abdominal pain, or headaches who visited Armed Forces Seoul District Hospital between January 2019 and December 2020. Critical illness was defined as a condition that required hospitalization, a procedure or surgery, or referral to a tertiary hospital. The symptoms and signs of critical illness were evaluated. RESULTS: Of the 762 enrolled patients, a critical illness was diagnosed in 45 patients (5.9%). Among chest pain signs, palpitation (odds ratio [OR], 22.8; 95% confidence interval [CI], 5.08-102.4; p < 0.001), exertional dyspnea (OR, 16.3; 95% CI, 3.38-78.8; p = 0.001), duration (> 5 minutes) (OR, 7.54; 95% CI, 1.93-29.49; p = 0.004), and squeezing type (OR, 5.28; 95% CI, 1.11-25.11; p = 0.037) were significantly associated with critical illness. Among abdominal pain signs, right-lower-quadrant tenderness (OR, 11.87; 95% CI, 4.671-31.87; p < 0.001) was an alarming sign. For headaches, criticality was low (1.5%), and half of patients with critical illness were diagnosed incidentally regardless of headache. CONCLUSION: We identified symptoms and signs significantly associated with critical illness in young male patients. This study might serve as a reference for deciding when to transfer soldiers in the field to a rear hospital, thereby contributing to the welfare and combat power of soldiers.