Cryptopatches (CPs) are part of the murine intestinal immune compartment, Cells isolated from CPs of the small intestine that were c-kit positive (c-kit(+)) but lineage markers negative (Lin(-)) gave rise to T cell receptor (TCR) alpha beta and TCR gamma delta intestinal intraepithelial T cells after in vivo transfer or tissue engraftment into severe combined immunodeficient mice. In contrast, cells from Peyer＇s patches and mesenteric lymph nodes, which belong in the same intestinal immune compartment but lack c-kit(+)Lin(-) cells, failed lo do so, These findings and results of electron microscopic analysis provide evidence of a local intestinal T cell precursor that develops in the CPs.