The most convincing argument against the hypothesis that persistent superlipophilic chemicals with log KOW >6, such as OCDD are bioconcentrated - if at all - to a low extent is that in all these bioconcentration experiments, except of 2,3,7,8-TCDD, exposure concentrations have been applied which exceeded water solubility by several orders of magnitude. In this paper, a indirect method for the estimation of bioconcentration factor (BCF) of OCDD is presented: The BCF value on a lipid basis (BCFL) of 8.5*107 in fish was obtained from an extrapolation fo a linear log/log relationship for kinetically measured BCFL data in fish and the OCDD concentration in the water up to water solubility of this chemical.