Chromosome analysis of ten patients with acute promyelocytic leukemia (APL) whom we observed in the last seven years revealed that nine patients (three males, six females) had t (15; 17) chromosomes, while fhe remaining one showed a normal female karyotype. Three of the cases with translocation had such additional chromosomal abnormalities as No. 8 trisomy, a No. 6 ring chromosome, and t (1; 9). The geographical distribution of the APL cases with t (15; 17) is uneven, exhibiting higher incidence in Kanto and Hokkaido areas in Japan. Of clinical findings, hepatomegaly less frequently seen in patients with APL was observed in six out of the nine patients with t (15; 17). Only one of those with translocation went into complete remission and the mean survival was 34 days except for the patient during remission, indicating that the patients with t (15; 17) respond poorly to treatment and the prognosis is poor.
