Transcriptional pathways controlling the development of CD44(hi) memory phenotype (MP) T cells with "innate-like" functions are not well understood. Here we show that the BTB (bric-a-brac, tramtrack, broad complex) domain-containing protein promyelocytic leukemia zinc finger (PLZF) is expressed in CD44(hi), but not in CD44(lo), CD4(+) T cells. Transgenic expression of PLZF during T cell development and in CD4(+) and CD8(+) T cells induced a T cell intrinsic program leading to an increase in peripheral CD44(hi) MP CD4(+) and CD8(+) T cells and a corresponding decrease of naïve CD44(lo) T cells. The MP CD4(+) and CD8(+) T cells produced IFNgamma upon PMA/ionomycin stimulation, thus showing innate-like function. Changes in the naïve versus memory-like subset distribution were already evident in single-positive thymocytes, indicating PLZF-induced T cell developmental alterations. In addition, CD1d-restricted natural killer T cells in PLZF transgenic mice showed impaired development and were severely reduced in the periphery. Finally, after anti-CD3/CD28 stimulation, CD4(+) transgenic T cells showed reduced IL-2 and IFNgamma production but increased IL-4 secretion as a result of enhanced IL-4 production of the CD44(hi)CD62L(+) subset. Our data indicate that PLZF is a novel regulator of the development of CD44(hi) MP T cells with a characteristic partial innate-like phenotype.