Three species of rats, Rattus exulans, R. rattus and R. norvegicus, and the house mouse, Mus musculus and certain species of birds and geckos were tested experimentally and in nature for their potential to serve as intermediate hosts of Toxoplasma gondii. Data reported herein, and from studies by others, indicate that common species of domestic rats are chronic carriers of the parasite and probably serve as a reservoir of infection for the cat, the apparent definitive host. The house mouse and certain species of birds are good experimental hosts, but more information on natural infection in these animals is needed. Infection could not be established in the gecko, but this animal may serve as a transport host. Experiments to evaluate the cockroach Leucophaea maderae as a potential transport host of Toxoplasma revealed that viable Toxoplasma oocysts, were harbored in the digestive tract of this cockroach, when starved, for as long as 20 days aiter it had fed on cat feces.