The development of stable antibody microarrays for the simultaneous detection and quantification of multiple tumor markers in blood, urine and tissue is proposed. The arrays will increase the diagnostic value of tumor markers in cancer diagnosis, assessment of treatment, and basic research in molecular profiling, by allowing the simultaneous measurement of multiple groups of markers associated with the same types of cancer. The key innovation is the use of an electrochemically grown matrix (iridium oxide) to immobilize antibodies and maintain their activity, and its application with well-established microelectrode array fabrication methods to produce stable protein microarrays. All the components can be readily miniaturized to circuit board level with very modest power requirements. The design of the arrays is such that they can perform electrochemical simultaneous multianalyte immunoassays (SMAI) from single, small volume samples. In Phase I we will demonstrate the simultaneous detection and quantification of two tumor markers, prostate-specific antigen (PSA) and carcinoembryonic antigen (CEA) using SMAI in order to provide proof-of-concept validation of our antibody microarray system. PROPOSED COMMERCIAL APPLICATION: Antibody arrays will be used to detect and quantify multiple tumor markets from body fluids or extracts of cancer tissues and cultured cells. Potential uses of cancer markers include screening in the general population, clinical staging of cancer, estimating tumor volume, monitoring response to therapy, detecting the recurrence of cancer and basic research in the molecular profiling of cancer.