Transcriptional competence of the interferon-gamma (IFN-gamma) locus is enhanced as Th1 effectors develop from naive CD4 T lymphocytes; conversely, this gene is repressed during Th2 differentiation. We now show that the Switch (Swi)-sucrose nonfermenter (SNF) component Brahma-related gene 1 (Brg1) is recruited, and positioned nucleosomes are remodeled, in a Th1-specific manner that is dependent on the transcription factor Stat4 and calcineurin phosphatase activity. Interference with specific components of mammalian Swi-SNF complexes decreased CD4 T cell differentiation into IFN-gamma-positive Th1 cells. These findings reveal a collaborative mechanism of IFN-gamma gene regulation during Th1 differentiation and suggest that a Th1-specific chromatin structure is created by early recruitment of Swi-SNF complexes and nucleosome remodeling dependent on Stat4 and calcineurin activation.