Since 1990 in Berlin the building blueprints and potaining documents for public utility buildings, in particular schools and child-care centres, have been serutinised and/or buildings have been visited for the possibility of the presence of elastic sealants containing PCB. Pursuant to this, samples of the sealing material of suspected buildings were examined and air in the rooms was measured. Results of measurements (n = 410) in community rooms of schools and child-care centres were an average value of 114 ng/m3 (maximum 7.360 ng/m3) and a geometrical mean of 155 ng/m3. For measurements in schools (n = 308), the geometrical mean was 229 ng/m3, whereas in child-care centres (n = 102) it was 48 ng/m3. Within the framework of the procedural method described above regarding the investigation of suspected buildings, about 15% of the school buildings and 3% of the child-care centres had indoor air values of over 300 ng/m3 (value indicating need for taking precautions) and 5% of the school buildings had more than 3.000 ng/m3 (the value warranting an intervention, according to the now defunct Federal Health Office). No values over 3.000 ng/m3 have been measured up to now in the community rooms of child-care centres. The investigations carried out throughout the Berlin Borough of Tiergarten of all school and child-care centre buildings yielded the results that about 13% of the schools and about 4% of the child-care centres had rooms with air values above 300 ng/m3. Only one school (4%), but none of the child-care centres investigated had values of more than 3.000 ng/m3. We are of the opinion that this proves the need for the creation of an on-target survey of the concrete pollution situation and short-term adoption of exposure-reducing measures or renovations. In any case the exposure of children to this toxicologically suspect substance by this additional way of pollution must be kept as low as possible. In addition to the description of a recently concluded PCB renovation in a school building, another indoor source of pollution is presented which was unknown to date. This is sealing material containing PCB which insulates the pipes of a heating system laid as an insulating floorcover strip near the wall. In the 21 classrooms of the school building, the indoor air concentration in 16 classrooms was 1.000-3.000 ng/m3 and in 5 rooms it was greater than 3.000 ng/m3, with a maximum value of 8.000 ng/m3. In addition, it could be proved for the first time that sealing materials containing PCB were used in the external joints of residential buildings and resulted in indoor air pollution of up to 1.000 ng/m3. The fact that the PCB was also found in sealants which were proved to have been processed even at the beginning of the 1990s, may be of special importance. Up to now, such recent use had always been excluded. Within the framework of the search for contaminated buildings, the time limit regarding the date of construction of the building is no longer adequate. It can be seen from this case in an exemplary fashion, that the removal of waste of the sealants (containing PCB) for the purpose of environmental care is still associated with great problems.