Immunoglobulin G (IgG) antibodies to moulds have been used as biomarkers of mould exposure, though their role reflecting exposure is not confirmed. The purpose of the present study was to evaluate the changes in mould-specific IgG antibodies in children during a 3-year follow-up in relation to changes in exposure, and to allergic and respiratory morbidity. In 1996, 212 primary school students with asthma, wheezing or prolonged cough participated in a clinical study, including clinical examination, skin-prick tests to 12 moulds and mould-specific IgG determinations to 24 moulds. In 1999, 144 students of the same cohort participated in an identical follow-up study; among them, mould-specific IgG was measured in 121 students. No association was found between IgG antibodies to moulds and exposure to moisture or moulds in schools. Likewise, changes in mould-specific antibodies were only weakly associated with changes in exposure. Mould-specific IgG antibodies had no significant association with asthma, wheezing or cough episodes. IgG antibodies to moulds seem to be poor markers of exposure among children exposed to moisture or moulds at school.