Abstract Introduction Obstructive sleep apnea (OSA) is a common condition and is more common in men with obesity and low testosterone (T). In men with OSA, T therapy is associated with the development of polycythemia (POLY). It has been shown that men with OSA have a higher risk of POLY with T therapy. Objective We aimed to identify the predictors of being at high risk for OSA in men presenting for low T assessment. Methods The study population included men undergoing low T assessment who completed the OSA risk assessment questionnaire, the STOP-BANG (SB). SB contains 8 questions: STOP (Snoring, Tiredness, Observed apnea during sleeping and high blood Pressure); BANG (BMI ≥ 35, Age ≥ 50, Neck circumference ≥ 17 inches, Gender). Each question is scored as yes (1) or no (0) and is scored 0-8. Using this score, patients are categorized as low risk of OSA (score 0-2), intermediate risk (score 3-4), or high risk (score ≥ 5 or ≥ 3 plus a BMI ≥ 35 or a neck circumference ≥ 17 inches). We also measured total T and free T levels, hematocrit (HCT), and recorded BMI and demographics. Multivariable analysis (MVA) was performed to define predictors of having a high risk of OSA. Parameters in the model included: age, comorbidities (hypertension, diabetes, dyslipidemia, coronary arterial disease), total T, HCT, and BMI. Receiver operating characteristic (ROC) analysis was performed to identify a BMI cut-off point associated with high risk OSA. Results 321 men were analyzed. Median age was 64 (56, 69) years. Median SB score was 4 (3, 5), 55% were high risk, 25% moderate risk, and 19% low risk. 46% had 2 ≥ comorbidities. 57% had T levels ≤300 ng/dL. Median total and free T were 281 (222, 373) and 7.5 (5.4, 10) ng/dL and median LH was 3.7 (2.2, 6.7). Median HCT was 44% (41, 46). 33% had HCT ≥ 45%, and 4% had HCT > 50%. Median BMI was 29 (26, 33) kg/m2 and 42% had obesity (BMI ≥ 30 kg/m2). On MVA, BMI and ≥2 comorbidities predicted high risk for OSA. ROC analysis showed cut-off point BMI ≥ 27 kg/m2 is associated with high risk for OSA by SB (sensitivity=0.8; specificity=0.6; AUC=0.77; p<0.001). For men with BMI ≥27 kg/m2, the rate of high risk OSA was 71%, versus 29% rate of high risk in men with BMI <27 kg/m2. Conclusions BMI ≥ 27 kg/m2 or higher and the presence of 2 or more comorbidities are the main predictors of high risk OSA. Disclosure No.