Employees are thought to lengthen their weekends by voluntary absenteeism, but the magnitude of such potentially reversible behaviour is not known. A follow up study based on employers' registers on the dates of work contracts and absences in 27 541 permanent full time municipal employees in five towns during 1993-7. The absence rate on each weekday separately for all sick leaves and for 1 day sick leaves was determined. 3.4% of the male employees and 5.0% of the female employees were on sick leave daily. The mean rate of sickness absence was lowest on Mondays, after which it increased towards Wednesday, and remained on the same level for the rest of the week. This pattern applied to both sexes, to each year of the follow up, and across towns, age groups, and income groups. For 1 day sick leaves, representing 4.5% of the total sickness absenteeism, the rates of sick leave for Mondays and Fridays were 1.4 and 1.9 times greater than those for other weekdays. However, these excess rates account for less than 1% of all days lost due to sickness absenteeism. Extended weekend absences were more common in men, in young employees, and in those in a low socioeconomic position, and they varied between towns. Extended weekends seem to contribute only marginally to the days lost due to sickness absenteeism.