ABSTRACT. Coelho C.D., Berto B.P., Neves D.M. & Lopes C.W.G. Periodicity and intensity of oocysts of the genus Isospora Schneider, 1881 shedding by passerines birds from wildlife trafficking and held in quarantine. [Periodicidade e intensidade de oocistos do gênero Isospora Schneider, 1881 eliminados nas fezes de passeriformes oriundos do tráfico de animais silvestres e mantidos em quarentena.] Revista Brasileira de Medicina Veterinária, 38(supl. 3):75-79, 2016. Programa de Pós-Graduação Ciência, Tecnologia e Inovação Agropecuá- ria, Pró-Reitora de Pesquisa e Pós-Graduação. Universidade Federal Rural do Rio de Janeiro. BR 465 Km 7. Campus Seropédica, RJ 23.897-970, Brasil. E-mail: email@example.com Diurnal frequency has been observed in species of intestinal parasites, especially in the genus Isospora Schneider, 1881 in wild birds, which shedding oocysts more often in the late afternoon. This study aimed to evaluate the periodicity and shedding oocysts by passerines birds maintained at the Center for Triage of Wild Animals, Seropédica, Rio de Janeiro, Brazil. Samples of one droplet of feces were collected from 602 passerine birds, in the morning between 9h and 12h and in the afternoon between 15h and 17h, from May to November 2010. Samples were diluted in potassium dichromate 2.5% 1:6 (v/v) and incubated at room temperature for seven days. Of each sample was also determined an OoPD (number of oocysts per defecation). Fecal samples collected in the morning had a lower number of positive samples (12/2%) in comparison with those collected in the later afternoon that they had a greater number of positive samples (136/23%), likewise OoPDs from birds of the families Cardinalidae, Emberizidae and Thraupidae were also different in intensity. Both results indicated that periodicity and intensity of oocysts shedding by passerine birds were extremely significant (p<0.0001) when they were determined by using late samples.