A small group (n = 12) of military white smoke munition workers provided blood plasma during a production break (S I) and after five weeks' production (S II) of a hexachloroethane (HCE)/titanium dioxide formula. Plasma was also obtained from a sex and age matched control group (n = 12) and a group (n = 13) of previously HCE-exposed workers, respectively. HCE in plasma (P-HCE) was determined with gas chromatography and electron capture detection. No HCE was found in the plasma samples from the two control groups. In the HCE exposed group the mean (+/- SD) P-HCE level increased almost two orders of magnitude from S I (0.08 +/- 0.14 microgram/l) to S II (7.30 +/- 6.04 micrograms/l) despite efforts to minimize the internal dose. Biological monitoring of HCE could be useful in occupational hygiene.