Aim of the study is to assess which traits characterize normal sleepers from "sleep extensors": the latter are normal adults who usually sleep 8-9 hours but are able to extend their sleep for about 12 hours when willing to do so. 100 healthy adults describing themselves as sleep extensors on the basis of a questionnaire and of actigraphic recordings are selected. Each subject completed the Eysenck Personality Questionnaire (EPQ), the Minnesota Multiphasic Personality Inventory (MMPI), the Morningness Eveningness Questionnaire (MEQ), the Epsworth Sleepiness Scale (ESS). These data were compared with those obtained from 100 normal sleepers by means of a discriminant analysis. Further, six sleep extensors and six normal sleeper have been poligraphically recorded. Discriminant analysis indicates that the circadian typology is the major trait discriminating the two groups, being the "sleep extensors" more evening types. A sleep phase delay could determine other two characteristics of "sleep extensors" pointed out in the present study: their lower sleep efficiency in the first part of the night and their higher sleepiness during the day with respect to normal sleepers. Finally, "sleep extensors" are characterized by a lower neuroticism's level.