There are two possible approaches to the prediction of subchronic or chronic toxicity using alternative methods. One is to extend the longevity of in vitro cultures to allow prolonged dosing. The challenge of this approach is to maintain not only the viability but the organ-specific properties of these cultures upon prolonged culturing. Various methods have been developed to extend the time that cultured cells remain viable for experiments, including the use of bioreactors, hollow fiber culture, perfusion culture, gel and collagen sandwich culture, reaggregating cell models, and 3-dimensional organotypic models. Another approach is to develop biomarkers for long-term effects based on acute exposure. High-content assays such as toxicogenomics, proteomics, and metabolomics are promising technologies for the discovery of these biomarkers. Information on these and other emerging research, methods, and policies for repeat dose toxicity testing will be provided on AltTox.org in the future; please check back again.