Seven mark-release-recapture experiments were conducted with a Wyeomyia mitchellii population in a wooded area near Vero Beach, Florida. Adult mosquitoes, marked with radiophosphorus during their fourth larval instar, were released once each month from March to October, 1977, either unfed or sugar-fed after emergence. Marked and unmarked adults were collected up to 100 meters distance from the release point in all 4 quadrants, with an average recovery rate of 5.2% in the 7 experiments. Dispersal was independent of the age of the mosquitoes at release time. Daily survival rates ranged from 0.76 to 0.87 for males and 0.74 to 0.91 for females, during different experiments. Marked unfed adults first fed on nectar after release and soon thereafter, started host-seeking, whereas sugar-fed females began host-seeking on the day of release. Almost all of the host-seeking females collected were inseminated. Host-seeking appeared to be continuous once started. Gravid females were collected from days 4 to 7 after emergence. Most females were parous from days 5 to 8. The average number of eggs in gravid females was 81 + 6.