Quinacrine dihydrochloride fluorescence patterns permit the identification of every normal human metaphase chromosome. To determine the effectiveness of the quinacrine fluorescence method in detecting and delineating reciprocal translocation chromsomes, individuals with such abnormal chromosomes were studied. The fluorescence patterns provided a means for the rapid identification of translocation chromosomes, many of which were extremely difficult or impossible to detect and identify by previous methods. Six patients had different translocations: (1) t(2p−;11p + ), (2) t(3p−; 18q + ), (3) translocation in which the arms of a No. 2 and a No. 6 had interchanged, (4) t(5p−;14q + ), (5) one in which arms of a No. 11 and a No. 17 were interchanged, and (6) t(1q−;18p + ). Studies by methods which do not permit such exact identification of all the chromosomes are no longer adequate in clinical cytogenetics.