The application of comparative genomic hybridization to DNA microarrays (array-CGH) has greatly improved the speed and resolution at which chromosome rearrangements involving genomic imbalance can be studied. For diagnosis of patients whose disease is suspected to be due to a balanced reciprocal translocation, we have developed a modification of array-CGH, termed array painting, which utilizes flow sorting of the derivative chromosomes before hybridization to an array to map the rearrangement breakpoints (Fiegler et al. 2003). However, current mapping resolution by array painting is rarely adequate to definitively identify disrupted genes which may be responsible for the disease phenotype and further time consuming and often technically challenging studies are required to clone and sequence the breakpoints. In this study, we describe the use of ultra-high resolution arrays to provide such an increased improvement in the resolution of breakpoint mapping by array painting that translocation breakpoints can be directly amplified and sequenced. This method of ultra-high resolution array painting enables rapid and definitive identification of gene disruption in balanced reciprocal translocations and will greatly improve the diagnosis for this group of patients.