Deletion on the long arm of chromosome 11 occurs in 5-20% of chronic lymphocytic leukaemia (CLL) patients. We analysed clinical-biological characteristics of 131 CLL patients carrying 11q deletion documented before therapy (de novo 11q deleted CLL). De novo 11q deleted CLL were characterized by high frequencies of unmutated immunoglobulin variable heavy genes, multiple fluorescence in situ hybridization aberrations and lymph node involvement. Factors significantly associated with shorter time to first treatment (TTFT) were advanced Binet stages, high white blood cell count, increased β2 -microglobulin levels, 17p in addition, splenomegaly and more extensive lymphadenopathy. We found that patients with