Functional analysis of the human genome, including the quantification of differential gene expression and the identification of polymorphic sites and disease genes, is an important element of the Human Genome Project. Current methods of analysis are mainly gel-based assays that are not well-suited to rapid genome-scale analyses. To analyze DNA sequence on a large scale, robust and high throughput assays are needed. We are developing a suite of microsphere-based approaches employing fluorescence detection to screen and analyze genomic sequence. Our approaches include competitive DNA hybridization to measure DNA or RNA targets in unknown samples, and oligo ligation or extension assays to analyze single-nucleotide polymorphisms. Apart from the advantages of sensitivity, simplicity, and low sample consumption, these flow cytometric approaches have the potential for high throughput multiplexed analysis using multicolored microspheres and automated sample handling.