Toxorhynchites rutilus rutilus (Coquillett) was successfully colonized and studied in the laboratory to determine the potential usefulness of the predatory species of mosquito as a biological control agent for container-breeding mosquitoes. When Tx. r. rutilus larvae were reared at 28 + 1 C in individual containers with a surplus of larvae of Aedes aegypti (L.) as prey, the duration of the immature stages averaged 1.6, 15.6 and 6.0 days for eggs, larvae, and pupae, respectively. Contrarily, with mass rearing conditions, the duration of the larval stage was significantly reduced to 11.1 days and pupation was more uniform than in individual containers. Adult females survive for 7 wk in laboratory cages and oviposit an average of 1 egg/day. Fourth-stage larvae of Tx. r. rutilus can survive for about 2 months without food. Adult females preferred to lay their eggs in water previously used to rear Ae. aegypti.