This paper critically reviews the evidence base for previously reported conceptual models of the development and persistence of insomnia. Although a number of perspectives have some empirical support, no one approach emerges as preeminent. Importantly, the efficacy of any particular psychological intervention cannot be taken as confirmation of presumed, underlying mechanisms. An integrated psychobiological inhibition model of insomnia is developed that accounts for the research data. The model views insomnia as arising from inhibition of de-arousal processes associated with normal sleep. It is proposed that sleep homeostatic and circadian factors are compromised by impairment of the automaticity and plasticity associated with good sleep, and that cognitive/affective processes activate the clinical complaint of insomnia. Common pathways for the action of cognitive-behavioral interventions are identified, and a research agenda is set for further conceptual and clinical study.