Using a new high-resolution technique for chromosomal analysis, we have successfully studied biopsy specimens of lymph nodes from 42 of 44 patients with non-Hodgkin's lymphoma and have categorized them using the new international histologic formulation and immunologic markers. Abnormalities of the clonal chromosomes were detected in all 42 patients. Three recurrent chromosomal aberrations were found to correlate with certain histologic types: a translocation between chromosomes 18 and 14 in 16 of 19 patients with follicular lymphomas (small cleaved cell, mixed cell, and large cell); a translocation between chromosomes 8 and 14 in 5 of 6 patients with small noncleaved-cell (non-Burkitt's) or large-cell immunoblastic lymphoma; and a trisomy 12 in 4 of 11 patients with small-cell lymphocytic lymphoma. Our findings suggest that characteristic chromosomal defects occur in certain lymphoma subtypes and that high-resolution chromosomal analysis promises to become an important tool in improving our basic understanding of lymphoid cancers. (N Engl J Med. 1982; 307:1231–6.) Standard cytogenetic techniques applied to cells obtained from biopsy specimens of lymph nodes frequently yield unsatisfactory results, with low mitotic indexes (0.001 to 0.1 per cent) and contracted chromosomes displaying poorly differentiated banding patterns (150 to 300 bands per haploid set). The results of previously published studies indicate that adequate cytogenetic analyses are possible in fewer than 70 per cent of all patients with lymphomas.1 Moreover, when chromosomal defects have been found, full characterization of them has frequently been impossible.1 2 3 Several investigators have reported nonrandom chromosomal abnormalities in lymphomatous nodes. However, these reports have generally described only a few patients. . .