The objectives of the study were (1) to analyze the distribution of TNF G-308A alleles among SIDS infants, SIDS parents, an unrelated adult comparison group, and ethnic groups with different incidences of SIDS; (2) to assess effects of virus infection and cigarette smoke on TNF-α responses; and (3) to assess the effect of gender, TNF G-308A, and cigarette smoke on responses to bacterial antigens (LPS and TSST-1) identified in SIDS infants. The gene discussed is TNF; the disease is sudden infant death syndrome.