Rhesus monkeys were inoculated with 10 5 PFU of biologically cloned human or mosquito LACV (LACV/human/ 1978-clone, LACV/mosquito/1978-clone). Each virus was inoculated intramuscularly (n = 4) or subcutaneously (n = 4). Blood samples were collected on days -7, 0, 2, 4, 6, 8, 10, 12, 14, 21, 28 post inoculation for blood chemistries, virus titration, and neutralizing antibody titration. Axillary or inguinal lymph nodes were surgically excised on days 4, 6, 8, and 12 post inoculation for viral titer or fixed in buffered formalin for histopathology and immunohistochemical analysis. Monkeys were observed daily for clinical disease. To determine LACV infectivity at low doses, rhesus monkeys (n = 4) were inoculated with 10 1 or 10 3 PFU LACV/mosquito/1978-clone subcutaneously. Blood samples were collected on days 0, 21, 28, and 42 post inoculation for neutralizing antibody titration.