A detailed lead isotopic and scanning electron microscope investigation of particulates from three houses in urban Sydney, previously decontaminated by their owners, has shown that they have been recontaminated over varying periods, as short as 6 months. The source of recontamination is lead paint from adjoining dwellings whose paint is thoroughly deteriorated, as well as from unknown sources. In one house, the external to internal lead loading was > 10:1. The pathway for the lead paint contaminants is both airborne and mechanical transport into the houses. Recontamination of houses provides an explanation for the maintenance of elevated blood lead levels in the children residing in these houses. Recontamination can be a major urban problem applicable in any community which used leaded paints on dwellings in the past. It is a matter of concern for families with young children and couples, especially women who are, or intend to become, pregnant.