In an effort to assess the utility of pretreatment cytogenetics as indicators of sites of involvement by lymphoma, clinical and cytogenetic correlations were performed on 133 consecutive specimens derived from 130 patients with non-Hodgkin's lymphoma. Nonrandom chromosomal aberrations detected at the time of diagnosis were associated with sites of clinical involvement presenting initially or during the progression of the lymphoma. Statistically significant associations included translocation breaks involving the chromosomal region 1p32-36 and bone marrow involvement, chromosome 14 abnormalities including breaks at 14q22-24 and splenic involvement, chromosome 9 abnormalities and pulmonary involvement, and monosomy 11 and bone involvement. A significant correlation was also observed between breaks involving the region 6q22-24, detected during the course of disease, and bone marrow involvement by lymphoma. The relationship of the sites of nonrandom chromosomal breakage reported here to known cellular oncogenes and implications to concepts of tumor evolution and spread are discussed.