The factors regulating dendritic cell (DC) development and homeostasis are incompletely understood. Here, we demonstrate that DCs express the lymphotoxin (LT)-β receptor (LTβR) and that in mice lacking the LTβR in hematopoietic cells, spleen, and lymph node, CD8⁻ DC numbers are reduced. B cells are a key source of LTα1β2 for splenic DC homeostasis, and transgenic overexpression of LTα1β2 on B cells leads to expansion of the CD8⁻ DC compartment. Furthermore, we find that about 5% of splenic DCs are undergoing cell division, and the number of dividing CD8⁻ DCs is disproportionately reduced in the absence of the LTβR. In parabiosis experiments, splenic DCs were only partially replaced by circulating precursors over a 6 week period. We conclude that LTα1β2 acts on DCs or DC precursors to promote DC homeostasis, and we suggest that DC proliferation is an important pathway for locally maintaining these cells in the steady state.