This field study assessed the effects of nighttime aircraft noise on actimetrically measured sleep in 400 people (211 women and 189 men; 20-70 years of age; one per household) habitually living at eight sites adjacent to four U.K. airports, with different levels of night flying. Subjects wore wrist-actimeters for 15 nights and completed morning sleep logs. A sample of 178 nights of sleep electroencephalograms (EEGs) were recorded synchronously with actigrams. The EEG was used to develop filters for the raw actigrams, in order to: (1) estimate sleep onset and (2) compare actigrams with aircraft noise events (ANEs). Actigrams, filtered to detect the onset of discrete movements, were able to detect 88% of all EEG-determined periods of interim wakefulness of > 15 seconds and periods of movement time of > 10 seconds. The main findings were: (1) actimetry and self-reports showed that only a minority of ANEs affected sleep, and, for most of our subjects, that domestic and idiosyncratic factors had much greater effects; (2) despite large between-site variations in ANEs, the difference between sites in overall sleep disturbance was not significant; (3) there was a diminished actimetric response to ANEs in the first hour of sleep and, apparently, also in the last hour of sleep; and (4) men had significantly more discrete movements than women and were more likely to respond to ANEs.