On April 22, 2011, the Q fever bacterium Coxiella burnetii was detected in a goat placenta collected from a farm in Washington, where 14 of 50 (28%) pregnant does had aborted since January. A county health alert advised health-care providers to ask patients with symptoms compatible with Q fever (e.g., fever, headache, chills, and myalgia) about exposure to goats, and the owners of the farm informed purchasers of their goats that C. burnetii had been detected in their herd. On May 25, the county health department reported a symptomatic patient with antibodies to C. burnetii who had purchased goats from the farm in February. On May 27, a report from Montana identified a child seropositive for C. burnetii whose family had purchased goats from the Washington farm in October 2010; one of the goats aborted triplets 2 weeks before the child's May 12, 2011, illness onset. On May 31, five more persons reported onset of symptoms compatible with Q fever from late March to mid-May, following exposure at a Montana farm to goats purchased from the Washington farm at various times during October 2010–January 2011. On June 10, the Washington State Department of Health and Montana Department of Public Health and Human Services requested CDC assistance to characterize the extent of the outbreak, distribute Q fever information, and identify others at risk for infection.