Background. "Kidskin" is an intervention study involving children at 33 primary schools in Perth, Western Australia. This study includes measurement of changes in implementation of schools' sun protection policies. This paper reports on measurement of observable aspects of sun protection.Methods. Hat use was assessed from videos of children in the playground. Shade use was measured using UVR sensitive polysulfone badges worn by a random sample of children. Shade provision was measured from aerial photographs of the schools. Principals were surveyed about school policies and practices.Results. Eighty-seven percent of children wore a hat during lunch time at school, although only 14% wore the most protective styles of hats. The mean proportion of ambient UVR exposure received by Year 1 children was 15.5%; children spent less time in the sun on sunnier days. On average, 14.5% of the playground was shaded; this was not associated with children's sun exposure. Correlations between these results and the principals' estimates were poor.Conclusions. Children should be encouraged to wear more protective styles of hats and to avoid sun exposure, even on less sunny days during spring and summer. Principals' estimates of shade provision and children's sun protection behavior at school are of little value. (C) 1999 American Health Foundation and Academic Press.