Lymphoceles after kidney transplantation are usually not infected and are drained into the peritoneal cavity, if their size requires treatment. Infected lymphoceles should be drained externally rather intraperitoneally, to avoid peritonitis. Ultrasonographic examinations of 2 febrile patients identified complex echoes that were correctly interpreted as infection within lymphoceles. The ultrasonographic diagnosis of infected lymphocele facilitates early and appropriate operative treatment.