Chelonia mydas is a sea turtle that feeds and nests on the Brazilian coast and a disease called fibropapillomatosis is a threat to this species. Because of this, it is extremely necessary to determine a methodology that would enable the analysis of blood leukocyte function in these sea turtles. In order to achieve this aim, blood samples were collected from C. mydas with or without fibropapillomas captured on the São Paulo north coast. Blood samples were placed in tubes containing sodium heparin and were transported under refrigeration to the laboratory in sterile RPMI 1640 cell culture medium. Leukocytes were separated by density gradient using Ficoll-Paque TM Plus, Amershan Biociences ® . The following stimuli were applied in the assessment of leukocyte function: Phorbol Miristate-Acetate (PMA) for oxidative burst activity evaluation and Zymosan A (Saccharomyces cerevisiae) Bio Particles ® , Alexa Fluor ® 594 conjugate for phagocytosis evaluation. Three cell populations were identified: heterophils, monocytes and lymphocytes. Monocytes were the cells responsible for phagocytosis and oxidative burst.Keywords: Chelonia mydas, green turtle, leukocytes, flow cytometry.A citometria de fluxo como ferramenta para avaliar a função celular de leucócitos sangüíneos de Chelonia mydas (Testudines, Cheloniidae) ResumoChelonia mydas é uma tartaruga marinha que freqüenta o litoral brasileiro para alimentação e nidificação e uma doença denominada fibropapilomatose é uma das mais importantes ameaças à sobrevivência dessa espécie. Desta forma, a definição de uma metodologia que permita analisar a função dos leucócitos sangüíneos torna-se extremamente necessária. Foram utilizadas amostras sangüíneas de C. mydas com e sem fibropapilomas capturadas no litoral norte do estado de São Paulo. As amostras sangüíneas foram colocadas em tubos contendo heparina sódica e transportadas em meio de cultura celular RPMI 1640 estéril e sob refrigeração.