Human granulocytotropic ehrlichiosis (HGE) is a tick-borne, acute, nonspecific febrile illness that was first described in 1994. At this writing more than 300 cases have been recognized in areas where the presumed tick vector Ixodes scapularis occurs endemically. Ehrlichiosis is a nonspecific influenza-like illness, and associated laboratory alterations are variable. Characteristic morulae (clusters of bacteria in leukocyte cytoplasm) can frequently be found in the cytoplasm of circulating neutrophils after careful inspection of the peripheral blood smear. The diagnosis is confirmed by demonstrating seroconversion to the HGE agent, positive polymerase chain reaction, or growth of the HGE agent in tissue culture. Doxycycline provides rapid and effective treatment.