A series of polychlorinated biphenyl (PCB) fires and explosion in PCB-filled capacitors and transformers is discussed. A sampling program followed by isomer specific determination of trace levels of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) is described. Data from a series of Swedish PCB accidents are given. In addition to PCDFs and PCDDs, we have also found a series of polychlorinated biphenylenes (PCBPs). Cleaning of contaminated areas was done by vacuum cleaning followed by high pressure washing.