Several informative combinations of viability and cytotoxicity chemistries are currently employed in HTS formats to mitigate false determinations. These multiplexes address systematic error caused either by disparate cell numbers delivered to assay wells or random compound interferences with reporter molecules [55] . Except in cases of cell-cycle arrest prior to loss of membrane integrity, or long term exposure models, measures of viability and cytotoxicity are inversely proportional (Fig. 5) . Therefore, non-conforming data sets can easily "flag" problem compounds for further analysis by orthogonal methods [57] .