Delayed sleep phase disorder is the most common of the circadian rhythm sleep disorders. Its treatment involves exploiting the intrinsic biological properties of the circadian pacemaker to advance biological rhythms, most notably the sleep-wake cycle, to a time which affords the individual an appropriate sleep opportunity compatible with normal societal functioning. This review highlights several new studies published in the last 18 months concerning sleep and circadian physiology relevant to the disorder and its management.In addition to new information regarding the epidemiology and associations of the disorder, the pathophysiological importance of light exposure across the entire day, with special relevance to the phase-delaying effects of artificial evening light, is being unravelled. Furthermore, disorder-specific differences in period length and sleep homeostasis are being considered as pathophysiological contributors to delayed sleep phase disorder. The molecular effects of chronic sleep deprivation and circadian misalignment are currently being explored as potential mechanistic markers of the deleterious health consequences associated with these states.Advances in our understanding of the dynamics of circadian physiology, sleep-wake regulation and the deleterious effects of misalignment and sleep deprivation, are spurring on efforts to find optimal treatment paradigms for patients presenting to sleep clinics with delayed sleep phase disorder.