Despite the wide attention given to the problem of truancy, empirical data on the extent of this phenomenon are limited. This article reports on a research project concerning the extent of allowed and disallowed absenteeism of pupils in 36 schools in four large Dutch cities. Truancy was determined at eight levels (for instance per school, per class and per subject) during 3 school days and 8990 lessons. The results show that the extent of allowed absenteeism (4.7%) is on average higher than the extent of disallowed absenteeism ( = truancy), that is 4.4%. The difference in the extent of truancy between schools is considerable. In schools with a division for lower vocational education more pupils play truant on average. This also holds for most of the older classes, Fridays, the first and the seventh to the tenth lesson and for job-oriented and commercial subjects. Relatively low truancy percentages were found for subjects that are frequently considered 'truancy subjects'. Most truants play truant for two lessons a day at most. On average 16% of a school's pupils play truant, though this percentage differs strongly between schools. Multiple regression analysis pointed out that the percentage of non-Dutch pupils, together with the average class size account for 56% of the variance in truancy rate.