Abstract Alert insomnia, the complaint of insomnia in the absence of measurable daytime sleepiness, has presented a theoretical enigma to sleep disorders professionals. Although it has been assumed that insomniacs are chronically sleep deprived, their lack of daytime sleepiness contradicts this assumption. Insomnia patients frequently complain of fatigue and other daytime symptoms that they attribute to poor nocturnal sleep. Yet, compared to noncomplaining controls, insomniacs have demonstrated neither daytime impairment nor a substantial deficit in nocturnal sleep time. In this article, we examine the data pertinent to the question of whether alert insomniacs are in fact sleep deprived, and we consider possible explanations for these findings. We also discuss the implications of these data for clinical management of these patients and for future research on insomnia.