The relation between the presence of readily visible man-made mineral fibre (MMMF) products in the ceilings and the presence/frequency of symptoms and diseases, and the correlation between the presence/frequency of symptoms and diseases and the concentration of MMMF in the indoor environment was investigated in 24 kindergartens. A combination of traditional epidemiological techniques and a technical analysis of a number of indoor air parameters did not support the hypothesis that release of MMMF from readily visible MMMF products in the ceilings was mainly responsible for the occurrence of symptoms or diseases related to indoor exposure in kindergartens.