Total flight times and flight numbers of Lambornella clarki Corliss & Coats-infected and uninfected nonblood-fed (control), blooded, and gravid Aedes sierrensis (Ludlow) were monitored in laboratory experiments using a free-flight acoustical system. Mean flight time and number of males were not affected by L. clarki infection, but mean flight time of infected females was significantly less than those of control and gravid females. Flight numbers of infected and control females did not differ significantly. Blood feeding initially suppressed flight, but flight dramatically increased with increasing time after the blood meal. There was an increase in flight that corresponded to increased parasite presence inside the ovaries in young, but not older, females.