The authors describe the sporogonic evolution of Hepatozoon caimani (Carini, 1909), in Culex dolosus (L. Arribálzaga). After describing the erythrocytic forms and the small schizogonic cysts with two merozoites, they show that the evolution of the parasite in mosquitoes is slow, taking about 24 days to form sporozoites at a temperature of 26-28ºC, and a relative humidity of 80-85%. Generally, two sporoblasts develop within the oocysts, one of them degenerating, while the other evolves and forms about 100 to 120 sporocysts, each containing from 15 to 20 sporozoites. No sporogonic evolution of the parasites has been achieved, neither in leeches (Haementeria lutzi) nor in "barbeiros" (Triatoma infestans).