Human plasmacytoid dendritic cells (pDCs) are major producers of IFNα, are activated by CpG motifs, and are believed to enter lymph nodes (LNs) via L-selectin dependent extravasation across high endothelial venules. To identify a similar murine DC type, CD11c⁺ cells in the LNs of L-selectin–deficient and control BALB/c mice were compared, revealing a population of CD11c⁺CD11b⁻ cells that is reduced 85% in the LNs of L-selectin–deficient mice. These cells are Gr-1⁺B220⁺CD19⁻, either CD4⁺ or CD8⁺, and localize within T cell zones of LNs. Freshly isolated CD11c⁺Gr-1⁺ cells express major histocompatibility complex class II at low levels, display a plasmacytoid morphology, and survive poorly in culture. Their survival is increased and they develop a DC-like morphology in interleukin 3 and CpG. Like human pDCs, CD11c⁺Gr-1⁺ cells stimulate T cell proliferation after activation with CpG and produce IFNα after stimulation with influenza virus. These cells also display a strain-specific variation in frequency, being fivefold increased in the LNs of BALB/c relative to C57BL/6 mice. These CD11c⁺CD11b⁻B220⁺Gr-1⁺ cells appear to be the murine equivalent of human pDCs.