Array CGH technology has allowed for a fine resolution mapping of the genomic aberrations that are characteristic of tumor cells. These aberrations can be driving factors in tumor genesis and progression, and as a result profiling them with array CGH has become very popular. We have developed statistical algorithms for the analysis of CGH data, from pre-processing to higher level analysis - with particular emphasis on the search for concordant aberrations across multiple samples. We will describe these methods and illustrate with examples.