Paraffin-embedded tissue samples from 30 cases of non-Hodgkin's lymphoma(NHL) and 10 of reactive hyperplasia, were processed for interphase cytogenetic chromosomal study. We performed non-fluorescent in situ hybridization(NFISH) using the enzymatic method with digoxigenin-labeled DNA centromeric probes for chromosome 7,12,18 and X, and a painting probe for chromosome 18. Chromosomal aberrations were observed in 27(90%) out of 30 cases of NHL. The most commonly observed numerical aberration was extracopy of X chromosome. There were some characteristic aberrations corresponding to each grade and group of NHL by International Working Formulation: In low grade NHL(9 cases), a third were associated with extracopy of chromosome 12, and disomy X was frequently found in small lymphocytic lymphoma(75%). With intermediate grade(16 cases), tetraploidy(25%), translocation of chromosome 18(25%), and extracopy of chromosome 18(19%) were characteristically associated. These results suggest that interphase NFISH is an easily performable method in retrograde cytogenetic study of archival materials. Some specifically correlated chromosomal aberrations corresponding to the histopathologic grades and groups could provide us more valuable information for determining pathologic diagnosis and assessing the clinical outcome of NHL.