To describe a considerably advanced method of array painting, which allows the rapid, ultra-high resolution mapping of translocation breakpoints such that rearrangement junction fragments can be amplified directly and sequenced. Ultra-high resolution array painting involves the hybridisation of probes generated by the amplification of small numbers of flow-sorted derivative chromosomes to oligonucleotide arrays designed to tile breakpoint regions at extremely high resolution. How ultra-high resolution array painting of four balanced translocation cases rapidly and efficiently maps breakpoints to a point where junction fragments can be amplified easily and sequenced is demonstrated. With this new development, breakpoints can be mapped using just two array experiments: the first using whole-genome array painting to tiling resolution large insert clone arrays, the second using ultra-high-resolution oligonucleotide arrays targeted to the breakpoint regions. In this way, breakpoints can be mapped and then sequenced in a few weeks.