Several studies have suggested that interleukin (IL)-8 can serve as a biomarker for discrimination of skin sensitisers from nonsensitisers. The authors established a stable THP-1-derived IL-8 reporter cell line, THP-G8, which harbours SLO and SLR luciferase genes under the control of IL-8 and glyceraldehyde 3-phosphate dehydrogenase promoters, respectively. After 6 hour treatment with chemicals, normalised SLO luciferase activity (nSLO-LA) was calculated by dividing SLO-LA by SLR-LA, and the fold induction of nSLO-LA (FinSLOLA) was calculated by dividing nSLO-LA of chem. treated cells by that of nontreated cells. The nSLO-LA of THP-G8 cells increased in response to lipopolysaccharide (LPS) and several sensitisers. The FInSLO-LA in THP-G8 cells induced by LPS or sensitisers correlated with their induction of IL-8 mRNA in THP-1 cells. The nSLO-LA value of THP-G8 cells was significantly increased (Fin-SLO-LA g1.4) by 13 of the 15 sensitisers as well as by 5 of the 7 nonsensitisers. Interestingly, pretreatment with N-acetylcysteine suppressed the increase in FInSLO-LA induced by all sensitisers (inhibition index (II) e0.8) but did not suppress that induced by most of the nonsensitisers. The authors then evaluated the performance of this assay using values of FInSLO-LA g1.4 and II e0.8 in at least two of three independent experiments as the criteria of a sensitiser, which resulted in test accuracies of 82% for the 22 chemicals used and of 88% for the chemicals proposed by European Centre for the Validation of Alternative Methods. This newly developed assay is a candidate replacement for animal tests of skin sensitisation because of its accuracy, convenience, and high throughput performance.