The use of polychlorinated biphenyls (PCBs) restricted to closed systems. They are thus still used as dielectric fluids in capacitors and transformers. The hypothesis that skin rashes and excema reported among datascreen operators might be caused by leakage of PCB from components in the screen terminals was investigated. No information about the chemical content of the electric components in the actual datascreen terminals were available. The PCB-concentration in the atmosphere in a workplace where such skin reactions had previously occurred was therefore determined. Air was sampled through 2 or 3 days, during work hours only. A glass fiber backed by an amberlite XAD-2 column was used to trap the sample. The total level of PCBs in this sample was analysed by glass-capillary gas chromatography with electron capture detection. Commercial PCB mixtures were used as standards. PCB-concentrations in the working atmosphere (56-81 ng/M3) were about 50-80 times the level of PCB in samples collected outside the building. Indoor and outdoor samples differed also qualitatively. The indoor samples contained only Aroclor 1242, while the outdoor samples contained a mixture of Aroclor 1242 and 1254. The amounts of PCBs measured were below the safety level for working atmosphere, as recommended by NIOSH in 1977. However, knowing that the samples were collected in an office where there was no known use of PCBs, the levels found were unexpectedly high. Further investigations should therefore be undertaken to clarify whether datascreen terminals might be sources of PCB-contamination.