This paper presents the results of a cytogenetic analysis on a patient with acute lymphocytic leukemia (ALL) type L2 according to the FAB classification. Of the metaphases examined, 69.3% belong to the aberrant clone of pseudodiploid karyotype. Marker chromosome 14q+ has been identified in all the cells of the clone. Duplication was found in 30% of the metaphases, and in 15% triplication of the proximal segment of the long arm of chromosome #1 (q11-q21). In one metaphase the long arm of chromosome #1 is made up of segment q11-q21 four times repeated. Aberrations of chromosome #1 support the idea that heterochromatic region may be related to the higher degree of the cell malignity.