Cytogenetic study of a short-term culture from a hibernoma, a very rare benign proliferation of the brown fat, demonstrated a four-break translocation t(5;7;11;17)(p14;q11.23;q13.1-13.3;p11.2) as the sole abnormality in all analyzed cells. Complex translocation involving band 11q13 have also been detected in the two other published cases of hibernoma. The consistent finding of 11q13 rearrangements appears to distinguish hibernoma from other benign adipose tissue tumors cytogenetically and suggests that 11q13 changes may play an important role in hibernoma pathogenesis.