Blood pressure (BP) varies over 24 hours. During normal sleep, BP typically decreases by 10% or more. Research suggests that disordered sleep, particularly sleep deprivation and obstructive sleep apnea, is associated with increased BP and risk of hypertension. Less is known about the relationship between insomnia and hypertension. Population-based studies have reported an association between insomnia symptoms and both prevalent and incident hypertension, particularly in the context of short sleep duration. Furthermore, a number of mechanisms have been proposed to explain the relationship between insomnia and hypertension. However, few studies have examined these proposed mechanisms, and even fewer clinical trials have been conducted to determine if improved sleep improves BP and/or reverses a nondipping BP pattern. Methodological concerns, particularly with respect to the diagnosis of insomnia, no doubt impact the strength of any observed association. Additionally, a large majority of studies have only examined the association between insomnia symptoms and clinic BP. Therefore, future research needs to focus on careful consideration of the diagnostic criteria for insomnia, as well as inclusion of either home BP or ambulatory BP monitoring. Finally, clinical trials aimed at improving the quality of sleep should be conducted to determine if improved sleep impacts 24-hour BP.