The diurnal pattern and oviposition behavior of Toxorhynchites theobaldi natural populations were studied in 25 artificial containers in the field. The mosquito exhibited a bimodal oviposition pattern with the lower peak at 1100 hr and a mean of 15.7 eggs per container. The higher peak was observed at 1900 hr with a mean of 80.9 eggs per container. Each female flew from 21 to 58 elliptic vertical circles before ejecting one egg upon the surface. In 270 oviposition events, the average was 31.4 ellipses, and the frequency distribution of flights number with different ellipse numbers was fitted to a Poisson distribution. There was a significant linear correlation (r = 0.70) between the oviposition rate and the container surface area.