A novel interleukin-2 (IL-2) dependent leukemia cell line MOTN-1 was established from the peripheral blood of a 63-year-old woman with T-cell large granular lymphocyte (LGL) leukemia in chronic phase. Primary peripheral blood leukemia cells were CD3+, CD5+, CD7+, CD56+, CD94+, CD161+, TcRαβ+, and HLA-DR+. The immunoprofile of the established cell line MOTN-1, however, showed CD3−, CD5−, CD7+, CD56+, CD94+, CD159+, CD161+, TcRαβ− and HLA-DR+; the MOTN-1 cells were cytoplasmatically positive for CD3ε and the products of the T-cell receptor ( TcR) genes β and γ. While the TcRβ and TcRγ genes were rearranged, the TcRδ gene was found to be deleted. DNA fingerprinting and chromosome analysis identifying the t(2;6)(q?23;q?21) and t(12;18)(q13;q?22) alterations demonstrated the authenticity and the malignant nature of the cell line. The scientific significance of MOTN-1 lies in (1) the rarity of this type of leukemia cell lines, (2) the co-expression of various T- and natural killer (NK)-cell-associated markers, and (3) its unique chromosomal aberrations.