Ultraviolet (UV) exposure is the major environmental factor involved in the development of skin cancers and occurs mainly during outdoor activities. During summer schools, children receive regular and significant solar ultraviolet erythemal radiation (UVER) while practising outdoor activities. Personal dosimeters (VioSpor) were attached to the shoulders of schoolchildren and used to quantify their exposure to UVER. The study took place in Valencia, Spain, during July 2008, with three age groups (7-8, 9-10 and 11-12 years old) and involved about 15 schoolchildren. The median (25, 75 percentiles) twice-daily UV exposure values for all groups was 5.49 (3.59, 8.00) standard erythemal doses (SEDs), where 1 SED is defined as effective 100 Jm(-2) when weighted with the CIE erythemal response function. Exposure ratio (ER) is defined as the ratio between the personal dose on a selected body site and the corresponding ambient dose received on a horizontal plane during the same exposure period. The median (25, 75 percentiles) ER value for all groups in the study was 5.9% (4.1, 8.7).