There is now strong evidence from animal studies and, in humans, from epidemiological studies as well as from retrospective and prospective intervention studies, that obstructive sleep apnea (OSA) can cause persistent hypertension not only during sleep but during waking hours as well. There is also some evidence that habitual snoring alone, even without OSA, can do the same. Many of the hitherto unexplained epidemiological, clinical, biochemical, hematological, and physiological abnormalities seen in essential hypertension (EH) could be explained by the accompanying sleep related breathing disorders (SRBD). Many cases of resistant hypertension are probably due to SRBD. Recent studies show that SRBD are extremely common in EH but that the vast majority of patients with these sleep disorders are being missed by physicians who are treating the accompanying hypertension, even when the patients already have blatant symptoms of OSA. Recent investigations have shown that the probable reason for this underdiagnosis of OSA is lack of physician knowledge about the condition. This lack of knowledge is prevalent not only among family physicians, but among hypertension specialists and researchers in the field of hypertension as well. OSA is a common, easily diagnosed, and eminently treatable condition that is associated not only with disturbed sleep, loud snoring and excessive daytime sleepiness (which greatly increases the risk of traffic accidents), but also with hypertension, especially resistant hypertension, a broad range of cardiovascular problems, decreased sexual functioning, memory deficits, difficulty concentrating, and changes in personality and mood. It deserves much more attention by physicians treating hypertension than it is currently getting.