Two factors of critical importance to the adoption of in vitro alternative assays are the predictive potential of the assay system and its intra- and interlaboratory reproducibility. Many in vitro alternatives to animal testing have been proposed, but only a few of them have been subjected to interlaboratory validation studies in order to assess their reproducibility and relevance to in vivo data. The study described in this paper was designed to assess the shippability, reproducibility and relevance to in vivo data of the Advanced Tissue Sciences Skin2TM Dermal Model substrate in concert with Advanced Tissue Sciences' MTT Cytotoxicity Assay Kits. This 3-dimensional Dermal Model, which consists of several layers of human, foreskin-derived, metabolically active fibroblasts grown to form a tissue equivalent on nylon mesh, was used as the substrate to test the toxicity of 12 chemicals proposed by the Commission of the European Communities (i.e., toluene, n-hexane, 1-butanol, chloroform, sodium dodecyl sulfate, benzalkonium chloride, silver nitrate, tributyltin chloride, dibutyltin dichloride, 2-butoxyethyl acetate, acetaldehyde, and 2-methoxyethanol). Dermal Model kits and MTT Assay Kits were manufactured by Advanced tissue sciences (formerly Marrow-Tech) in the U.S. and shipped to Janssen Pharmaceutica in Belgium. Two runs of each of the twelve chemicals were performed in each lab one week apart and MTT-50 values were determined for each compound. The in vitro data were also compared with existing in vivo data and found to be highly correlative. Interlaboratory reproducibility was also excellent, demonstrating that the skin2 human Dermal Model product remains stable during intercontinental shipment and that the MTT Assay Kits, also supplied by Advanced Tissue Sciences, provide a standardized method for assessing the toxicity of test agents.