Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder. Although frequently undiagnosed, OSA is highly prevalent and presents most often with excessive daytime sleepiness (EDS). While obesity is the major predisposing factor, patients with OSA and EDS are at increased risk of other conditions, including cardiovascular disease, type 2 diabetes, cognitive impairment, and depression. Significant consequences include morbidity and mortality from the associated conditions in addition to personal and societal consequences of cognitive impairment, such as driving and workplace accidents. Primary care physicians are ideally placed to screen for OSA and EDS in patients who present with commonly comorbid conditions such as obesity, cardiovascular disease, metabolic syndrome, and depression. Conversely, treatment of OSA and associated EDS might help alleviate significant comorbidities and their clinical and societal consequences.