Obstructive sleep apnea (OSA) syndromes afflict various age groups. OSA is reported to be more prevalent in middle-aged men compared with women in the United States, but the true prevalence may be higher, because OSA syndromes are underdiagnosed. This article reviews the history of sleep apnea, discusses the clinical presentation of OSA-hypopnea and upper airway resistance syndrome, and presents the pertinent physical examination findings and the results of sleep laboratory testing. Associated significant comorbid conditions and treatment options are reviewed.