Polychlorinated biphenyls (PCBs) are 209 related compounds, a dozen of which are known as dioxin-like PCBs (dl-PCBs) and are among the most toxic PCBs. Polychlorinated biphenyls contribute to many adverse effects to human health, including cancer, and are a major cause of fish advisories in North America. It is a common perception that individual PCB compounds, especially dl-PCBs, rather than total PCB need to be quantified to predict the environmental hazard because of differences in their toxicity potential and distribution among various environmental matrices, including aquatic food webs. Because the current analytical methods for quantifying dl-PCBs are complex and four- to fivefold more expensive, limited fish samples are analyzed for dl-PCBs. Using what likely is the largest dl-PCB fish data set (n = 912) with a wide distribution of fish species (n = 22), size (19-112 cm), weight (100-14,300 g), sex (male:female, 51:49), and PCB contamination level (20-7,300 ng/g wet wt), we show that the comparatively less expensive and rapid measurements of total PCB in fish can be utilized to assess dl-PCB-related toxicological hazard, measured as 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQ). A regression equation of dl-PCB-related TEQ (i.e., TEQdl-PCB) to total PCB in fish is presented (TEQdi-PCB = [2.56 x 10(-5)]CtotalPCB, r = 0.89, p < 0.001). The regression was evaluated by applying it to three independent data sets of substantial sizes (n = 55, 141, and 176). The TEQdl-PCB estimated using the regression and total PCB measurements were within a reasonable factor of two to three of the TEQdl-PCB calculated from the dl-PCB measurements. The successful evaluation indicates versatility of the regression.