Viremia and antibody responses to La Crosse (LAC) virus were determined for juvenile, subadult and adult chipmunks (Tamias striatus). Viremia was detected in 16 of 16 juveniles, 13 of 17 subadults and 21 of 29 adults fed upon by transovarially (TO)-infected Aedes triseriatus. Mean viremia titers for juvenile, subadult and adult chipmunks responding to LAC infection were 3.0, 2.9 and 3.2 log10SMICLD50/0.025 ml, respectively. The average duration of viremia with LAC virus was 2.4, 2.3 and 2.4 days for juveniles, subadults and adults, respectively. Mean viremia titers and durations did not differ significantly among chipmunk age-classes. Neutralizing antibodies to LAC virus were detected in viremic chipmunks at day 5 and day 20 post-infection. Observations of TO-infected Ae. triseriatus and their sibling controls refeeding on restrained chipmunks indicated that a significant number of infected (34/54) and uninfected (37/59) females probed multiple times to obtain a second bloodmeal. Data indicate that chronological age or time between successive bloodmeals affects feeding behaviors. No relationship between probing or ability to refeed and infection was found.