An experimental study of nematode endophthalmitis due to T canis and review of the literature has been presented. Six owl monkeys were infected either by nasogastric tube using embryonated T canis eggs or by carotid or intravitreal injection of second stage larvae. The clinical manifestations, especially ocular, were observed and various diagnostic tests performed. Only minimal or no intraocular changes were seen after systemic infection but significant abnormalities such as retinal hemorrhages and venous dilation were noted after intravitreal infection. Motile larvae were observed in the lenses of three eyes and in the vitreous of five eyes and, probably a sixth, after intravitreal injection. The intensity and timing of the intraocular reaction seemed to correlate with the infecting dose and apparent disappearance of larvae from the eye. Pathologic confirmation of larvae in the lens was obtained in one eye. A marked inflammatory reaction occurred in eyes receiving intraocular infection but none was seen in eyes with only systemic infectin. Various laboratory and serologic studies were performed, including the ELISA test, which were used to evaluate systemic as well as intraocular responses to infection with T canis. The two monkeys infected by nasogastric tube gave a positive ELISA response in the serum but intraocular fluids gave a negative response in all monkeys including those infected syst:mically and/or intraocularly. Problems in the understanding of clinical aspects of the disease, laboratory diagnosis and treatment are discussed. The need for future experimental studies is emphasized.