Background: Obstructive sleep apnea hypopnea syndrome (OSAHS) is a life threatening breathing disorder diagnosed by overnight polysomnography (PSG). As PSG is expensive and has limited availability, this study was done to establish the effectiveness of the Adjusted Neck Circumference Score (ANCS) as a diagnostic measure in early detection of OSAHS. Methods: 427 patients were included in a retrospective study, they actually performed full-night PSG study, reviewing Epworth sleepiness scale (ESS) questionnaire, STOP-BANG score, BMI, Neck circumference (NC), Apnea Hypopnea Index(AHI) and ANCS which is composed of: NC, presence of snoring, evidence of nocturnal gasping or choking and presence of hypertension Results: The current study included 427 patients, 396 (92.7%) were diagnosed as OSA (Group I) and 31 (7.2%) patients were non-OSA (Group II). NC of 40.5 cm can differentiate OSA cases from non OSA with sensitivity 72%, specificity 41.9%, accuracy 69.9%, PPV 94.1% and NPV 10.5% while ANCS could diagnose OSA cases with sensitivity 83.8% and exclude 54.5% of non OSA cases at cut off value of 42.5 , accuracy of 81.5%, PPV 95.9% and NPV 20.7%. Also, ANCS can predict severe OSA by 79.8 % at 44.5 cut off value, with specificity 54.9% and accuracy 70.2%. Conclusion: ANCS is considered a simple clinical measurement for early detection of OSA and its severity at outpatient department. Also, ANCS has higher specificity, sensitivity and accuracy than NC in clinical diagnosis of OSA.