During August 22-26, 2003, four injection-drug users (IDUs) in Yakima County, Washington, sought medical care at the same hospital with complaints of several days of weakness, drooping eyelids, blurred vision, and difficulty speaking and swallowing. All four were regular, nonintravenous injectors of black tar heroin (BTH), and one also snorted BTH. This report summarizes the investigation of these cases, which implicated wound botulism (WB) as the cause of illness.