After the introduction of the dengue-2 (16681) virus by intradermal (i.d.) injection into the footpads of mice, Langerhans cells (LCs) increased in numbers within 24 h at the site of injection and neutralising antibody developed. On comparing the i.d. and intramuscular (i.m.) routes, antibody was produced more rapidly and at higher levels when the virus was injected by the i.d. route. Subsequent re-challenge by the i.d. route produced an even more rapid serological response with all mice producing significant neutralising titres within 12 h. Numbers of ATPase-positive LCs varied with time. A significant sharp drop in LC densities in the early post-injection phase directly correlated with the increased numbers of dendritic cells in the superficial dermis and interfollicular sinuses of draining lymph nodes (LN). Immunofluorescence showed the presence of viral antigen in the footpad epidermis and draining LN within minutes or within 2 h of challenge, respectively.