Since its first description in human beings in 1986, ehrlichiosis is now increasingly recognized as a cause of tick-borne febrile illnesses. However, the disease has been reported only rarely in immunosuppressed patients. We report a case of human ehrlichiosis in a patient with a cadaveric renal transplant. The diagnosis was confirmed initially by a positive polymerase chain reaction (PCR) for E. chaffeensis. The antibody titer became positive several weeks later. The patient responded promptly to treatment with doxycycline. Ehrlichiosis should be considered in the differential diagnosis of an acute febrile illness in transplant recipients. PCR provides a rapid means to confirm the diagnosis, particularly in settings in which antibody response may be suppressed.