Our goal was to develop a fast-screening bioassay to determine dioxin levels in the environmental and biological samples from dioxin-contaminated areas. Our original dioxin-responsive-element (DRE)-driven luciferase bioassay (using Huh7-DRE-Luc cells) was modified by reducing the incubation temperature of the cell culture from 37 to 35°C and by adding phorbol-12-myristate-13-acetate, and the modified bioassay was used to examine samples from soil, sediment, and fish. The results of this bioassay were shown to be significantly related to those of the high-resolution gas chromatography/high-resolution mass spectrometry assay of dioxins. The correlative equation was: log (PCDD/Fs I-TEQs) = 1.19 × log (BEQs) - 1.15 with R(2) = 0.95 (p < 0.001).