Francisco de Paula Fajardo Júnior was a pioneer of microbiology and tropical medicine in Brazil. Born on February 8, 1864, in Santa Maria Madalena, in the north-central part of Rio de Janeiro State, he graduated from the Rio de Janeiro School of Medicine in 1888 with a medical thesis on hypnotism, a first in Brazil. A renowned practitioner of medicine, he was appointed assistant to clinical propaedeutics in 1892, a chair then held by Francisco de Castro. He also taught at the Free People’s University and headed the Bacteriology Laboratory at the Federal Sanitary Institute. He devoted much of his career to researching the malaria parasite and became one of Brazil’s leading authorities on the topic. He also studied cholera morbus, beriberi, bovine piroplasmosis, and avian spirochaetosis. He died early, reportedly of anaphylaxis, on November 6, 1906, at the age of 42, after inoculating himself with plague serum made at the Oswaldo Cruz Institute.