Gene expression has been analyzed by throughput DMA microarrays which simultaneously monitor the expression of thousands of genes. However, mRNA expression of a gene may not correlate with protein expression because of the differences in rates of mRNA translation/degradation and post-translational modification. Mass spectrometry with/without prior separation of proteins has been developed but the burden of the experiment is on the user. During Phase I, we successfully developed and commercialized rat drug-metabolizing enzyme antibody microarrays containing 76 antibodies for cytochromes P450 and co-enzymes, phase II drug-metabolizing enzymes, apoptosis-related proteins, house-keeping proteins and Flag internal control protein. During Phase II, we will (1) further improve rat polyacrylamide-based hydrogel arrays, (2) improve and develop additional arrays with chips coated with various surface materials, (3) develop and explore signal enhancing methods, (4) develop mouse drug-metabolizing enzyme antibody microarrays, (5) develop human drug-metabolizing enzyme antibody microarrays and (6) explore utility of antibody arrays and discover markers for 5 classes of toxicants. The targeted arrays produced with form-specific antibodies of closely related proteins involved with drug and environmental toxicant metabolism will be an invaluable tool for toxicoproteomics.