Title: Hierarchical models approach for detecting gene copy number changes Abstract: Array comparative genomic hybridization (CGH) is a technology used to detect DNA copy number alterations which help identify the relevant genes for cancer development. This recent technology development calls for new statistical methods for analyzing array CGH data. Here we propose a Bayesian method to analyze multiple samples at the same time. Our method is based on hierarchical model with samples grouped according to the disease progression and survival status. The posterior probabilities of copy gain/loss are estimated for each gene at the group level. From that result, we can also classify new patients and identify the genes relevant to the group difference. We will demonstrate our method on simulated and real data sets.