鈥� Sleep polygraph and questionnaire data of 18 chronic primary insomniacs were compared with those of 18 age- and sex-matched controls. The insomniacs had significantly longer sleep latencies, less total sleep, less sleep efficiency, more terminal wake time, and less delta sleep. There were significant discrepancies between the insomniacs' and controls' subjective assessments of their sleep and the sleep-polygraph data, but in opposite directions. The insomniacs' recorded sleep also showed more night-to-night variability than that of the controls. However, the controls, in contrast to the insomniacs, reported sleeping worse in the laboratory than at home. Significant differences between insomnia subtypes validly reflected the insomniacs' subjective complaints and were generally in accord with expectations based on them.