Prof Charles Perou talks to ecancertv at the 2010 San Antonio Breast Cancer Symposium about next generation sequencing and whole genome sequencing and their application to breast cancer. He discusses using sequencing technology to study gene expression, and how that compares and contrasts with micro array studies on human breast cancer specimens. This allows assessment of both genes and their mutations, and thus potentially much greater accuracy of treatment and assessment of risk. Analysis of the data is extremely time consuming; advances in computing in the next few years are likely to help with clinical application.