Twelve cases of T gamma LPD (lymphoproliferative disorders of Fc gamma receptor-bearing T cells) involving an expansion of large granular lymphocyte/natural killer (LGL/NK) cells were investigated for the expression of LGL/NK-associated markers and for T beta gene rearrangement. All the cases selected were classified as T gamma LPD on the basis of morphology, function, and phenotype of the circulating cells. 10 to 12 cases displayed clonal rearrangements of the T beta locus and expression of the T3 antigen, whereas the 2 remaining cases displayed the germline configuration of the T beta gene and no expression of the T3 antigen. T8, Mol, B73.1, and N901 antigens were variably expressed among both T beta+T3+ and T beta-T3- T gamma LPD cases. We suggest that individual T gamma LPD cases represent the clonal expansion of cells frozen at different stages of differentiation/activation within an individual hematopoietic LGL/NK lineage.