Familial B-cell chronic lymphocytic (B-CLL) leukemia has been defined as an entity epidemiologically different from sporadic B-CLL. Cytogenetic abnormalities in familial B-CLL, studied either by conventional cytogenetics or by interphase fluorescence in situ hybridization (i-FISH), have rarely been reported. We report a two-case family affected with B-CLL showing two different abnormal karyotypes detected by conventional cytogenetics [46,XX,del(7)(q32) and 46,XY,add(1)(p36),del(6)(q21)] but sharing a del(13)(q14) at the D13S319 locus, detected by interphase fluorescence in situ hybridization.