OBJECTIVES: This study aimed to standardize an "in house" immunoassay to detect anti-Toxocara IgG antibodies in human serum to estimate the seroprevalence of Toxocara infection, and to identify its potential risk factors in children living in poor areas of Salvador, a large northeastern Brazilian city. METHODS: Parents of 1309 children answered a questionnaire containing possible risk factor for acquisition of this infection. Blood was collected and the presence of anti-Toxocara IgG antibodies was detected by indirect ELISA using T. canis larval excretory-secretory antigens in sera previously absorbed with Ascaris lumbricoides antigens. RESULTS: Seroprevalence of Toxocara infection was 48.4%. Children's age, low maternal schooling, contact with dogs and cats, and household located in paved streets were shown to be risk factors for Toxocara infection. CONCLUSIONS: The seroprevalence of Toxocara infection is high among children living in a poor urban setting of Brazil. The association of low maternal education with higher Toxocara infection supports studies showing that low socioeconomic status is a risk factor for the acquisition of this infection as a reflection of hygiene habits of the family. And both infected-dogs and cats may be involved in this parasite transmission in this children population.