Seven investigations of suspected foci of amebiasis between October 1971 and June 1974 lead to three conclusions. (1) A number of laboratories have vastly overdiagnosed amebiasis and have reported leukocytes in stools as Entamoeba histolytica. Two laboratories found to be in error were in community hospitals, and one was at a teaching hospital associated with a medical school and a school of public health. These three laboratories had been diagnosing more than 1200 cases of amebiasis a year for 20 years. (2) When amebiasis does occur, it is likely to be misdiagnosed. In one outbreak with four cases and three deaths, amebiasis was not diagnosed until two patients had died and another was critically ill. Sporadic cases may be mistakenly diagnosed as ulcerative colitis and inappropriately treated with steroids. (3) Foci of endemic amebiasis continue to exist in the United States, both in institutions and in noninstitutional settings.