Recent reports from countries with a highly developed economic status point out the association of well-being of children with socio-economic factors. The aim of the present investigation was to examine the extent to which health problems, i.e. functional impairments, diseases and handicaps, in 4-year-old children are related to socio-economic factors. The analysis was based on data from 7 173 children who had undergone the routine general health screening of 4-year-olds in the county of Uppsala. In the statistical analysis the main emphasis was laid on an explanation of the variance on the individual plane. The results showed that the correlations between health problems and socio-economic factors in general were weak or non-existent. An explanation of the lack of correlation in our sample might be that Sweden had succeeded in largely eliminating the health problems associated with external living conditions of the family. If differences between population groups do exist--and in the light of findings from other investigations it seems highly probable that they do--then these differences are probably to be sought in families' way of functioning, in the internal and external pattern of communication, in the general emotional climate and in the degree of social integration in the society.