Paradichlorobenzene has been used extensively as a household moth control agent and as a deodorant for many years, and it is considered to be safe and suitable for these purposes. However, cases of poisoning attributed to paradichlorobenzene have been reported. A convenient method for determining exposure to this halobenzene is important in evaluating any hazards involved in its use. The halobenzenes are metabolized mainly by oxidation to phenols, quinols, catechols and related compounds, or by forming mercapturic acids. This paper describes a method which successfully employs gas chromatography with electron capture detection for the measurement of PDB and its major metabolites.