Clinical management of human cancer is dependent on the accurate monitoring of residual and recurrent tumors. We have developed a method, called personalized analysis of rearranged ends (PARE), which can identify translocations in solid tumors. Analysis of four colorectal and two breast cancers revealed an average of nine rearranged sequences (range 4 to 15) per tumor. Polymerase chain reaction with primers spanning the breakpoints were able to detect mutant DNA molecules present at levels lower than 0.001% and readily identified mutated circulating DNA in patient plasma samples. This approach provides an exquisitely sensitive and broadly applicable approach for the development of personalized biomarkers to enhance the clinical management of cancer patients.