Microarray is the more mature gene analysis techniques so far, which can allow high throughput analysis of the function of many genes. Microarray can be used to understand the disease mechanisms and is also very useful to improve disease diagnosis, disease classification, prognosis evaluation and to improve treatment outcome. In this project, we use oligo microarray to genome-wide profile the altered gene expressions in peripheral blood mononuclear cells of OSAS patients; and to correlate the dysregulations of gene expression with the clinical outcome. We will also examine the gene expression patterns change before and after treatment with CPAP. The information obtained by this approach will be very useful to understand the pathogenic mechanism of OSAS that leads to the systemic and cardiovascular complications. Further therapeutic intervention may therefore be possible.