The NUP98 gene is involved in several chromosomal abnormalities associated with acute leukemia. The recurrent t(11;20)(p15;q11) chromosomal translocation results in generation of the NUP98/TOP1 chimeric gene. This abnormality has been observed primarily in therapy-related leukemias, and TOP1/NUP98 transcripts have not been demonstrated. We describe a case of de novo acute myeloid leukemia with t(11;20)(p15;q11), with no known history of exposure to chemicals. The translocation occurred in intron 13 of NUP98 and intron 7 of TOP1, as in the three previously reported cases. The breakpoint in NUP98 was exactly the same as that found in a previously reported case. In addition, a reciprocal TOP1/NUP98 transcript was detected for the first time in our patient.