Hazardous biochemical agents in indoor animal husbandry environments promote the occurrence of various illnesses among husbandry workers and industrial animals. The relationship between endotoxin levels in dust collected from Korean beef cattle farms and markers of bovine cellular immunity was investigated. Peripheral blood was obtained from 25 cattle from five cattle farms in Korea. Endotoxin levels present in total or respirable dust were determined by the Limulus Amebocyte Lysate Kinetic method. Cytokine production was evaluated following the stimulation of peripheral mononuclear cells with concanavalin A for 72 h in a 5% CO₂ incubator. Production of both interleukin (IL)-4 and interferon (IFN)γ was significantly higher in the high endotoxin exposure group (100.9±70.6 EU/㎥) compared with the low endotoxin exposure group (17.7±18.6 EU/㎥), with a lower IFNγ/IL-4 ratio in animals from the high endotoxin farms, indicating immunity skewed toward a type-2 response. The proportion of γδ T lymphocyte, important bovine immune cells involved in protection against microbial infection, was lower in cattle from the high endotoxin farms than in those from the low endotoxin farms. The numbers of white blood cells, red blood cells, lymphocytes, eosinophils, and basophils were significantly downregulated in cattle from the high endotoxin farms. Overall, these results suggest a probable negative association between dust endotoxin levels and cell-mediated immunity in Korean beef cattle.