Microarrays or microchips represent a new area of high technology, which will completely change the methodological approach to basic research and clinical diagnostics. This technology can be used for genotyping, expression profiling and proteome analysis. Genetics and molecular medicine have an expanding need for rapid genotyping, mutational analysis and DNA re-sequencing technologies, i.e. microarrays that have a clear potential for miniaturization, parallelization, and automation and enable high-throughput screening. Expression profiling technology is a new tool for investigating expression patterns, identifying new disease genes either for monogenic disorders or for complex traits, identifying new functional and cellular relationships and identifying new pathways and possible related drugs. This technology has been successfully applied to the study of complex traits, i.e. cardiovascular diseases, cancer and type II diabetes, providing new insights into possible pathogenetic mechanisms and new therapeutical approaches. Finally, microarray can further improve proteome analysis. This review discusses these points.