1. Hexachlorobenzene (HCB) internal dose in the general population of Barcelona (Spain) was estimated after new indications of the carcinogenicity of this chemical in humans were recently reported. Hospital blood bank facilities and randomly selected volunteers were used for HCB analyses in serum (n = 100) and cerumen (n = 25). Other main organochlorine residues often found in human tissues and blood (pp DDE, beta-HCH,) were also determined. 2. HCB serum levels currently found (Range 0.7-19.7 ng Ml-1; X +/- s.d.: 4.13 +/- 3.61; GM: 3.05) were compared to those found in a similar survey made in 1986 on the same population. The serum HCB levels showed a significant decrease (P < 0.001) when compared to the former results and correlated with age (P < 0.001) suggesting a progressive preponderance of a stable blood-adipose equilibrium with fewer variations due to recent and variable intake of the chemical. 3. Cerumen analyses revealed detectable concentrations of HCB in all samples (Range: 160-4790 ng g-1 in extractable lipid basis) and confirmed the suitability of this matrix to assess the body burden of residues accumulated in adipose and lipid-rich tissues. The set of results shows that, although HCB exposure has been reduced, the overall population under study still accumulates significant amounts of this possible carcinogen.