Fluorescence in situ hybridization (FISH) was used to detect 6q-, 11q-, +12, 13q-, 17p- and translocations involving 14q32 in interphase nuclei from blood and/or bone marrow from 113 patients with B-cell chronic lymphocytic leukaemia (B-CLL). A total of 87 patients (77%) had a FISH anomaly: 13q- x 1 was most frequent (64%) followed by 13q- x 2 (28%), +12 (25%), 11q- (15%), 17p- (8%) and 6q- (0%). FISH results for blood and bone marrow cells in 38 patients were similar. Purified CD5+/CD19+ cells from blood were studied in eight patients and results indicate that in some patients not all B cells have FISH anomalies. We used a defined set of hierarchical FISH risk categories to compare FISH results by stable versus progressive disease, age, sex, Rai stage, CD38+ expression and IgVH mutational status. Significant differences in FISH risk distributions were associated with Rai stage, disease status and CD38+, but not by age, sex or IgVH mutational status. To look for baseline factors associated with high-risk disease, multivariate analysis of age, sex, Rai stage, CD38+ and disease status versus FISH risk category was performed. Importantly, only CD38+ was significantly associated with high-risk FISH categories (+12, 11q- and 17p-) after adjustment for the effects of other variables.