Nocturnal wanderings, especially when they occur in adults, have provided endless fascination, fear, perplexity, and occasional bemusement. Most often, nocturnal wanderings in adults are sleepwalking (SW) episodes. Frequent, chronic, and/or potentially injurious SW in adults is a parasomnia that usually begins as an incomplete arousal from non-rapid eye movement (NREM) 3 sleep. SW occurs at a peak age of 8–12 years, only a quarter continue beyond age 13 years. Epidemiological studies suggest that 2–4 % of adults sleepwalk at least once a year, but less than 0.5 % walk frequently. Most have a history of SW as children. Complex motor behaviors during sleep (such as eating, driving a motor vehicle, or sexual behavior) may be a variant of SW, but must be distinguished from other causes (e.g., rapid eye movement (REM) sleep behavior disorder, parasomnia overlap syndrome, drug impairment, dissociation, and even malingering). SW in adults tends to be chronic, often a persistence or recurrence of childhood SW, but then precipitated, primed, and/or triggered by a host of factors that impair arousal and deepen and fragment NREM 3 sleep. Other primary sleep disorders (especially obstructive sleep apnea, restless legs, or a circadian rhythm disorder) can precipitate or exacerbate SW, especially in individuals with a familial or genetic susceptibility for it. Video-polysomnography (PSG) is usually indicated. Treatment of SW consists of reassurance, education of the patient and family, setting up a safe sleep environment, identifying and treating other sleep disorders, and reducing or avoiding priming or precipitating factors. Video-PSG findings and indications for pharmacotherapy are reviewed.