Unpasteurized milk from a farm in Cowlitz County, Washington, was consumed by persons who had participated in a cow-share program and was the source of an E. coli O157:H7 outbreak. Persons purchased interests in, or shares of, dairy cows in return for a portion of the milk produced. The sale of raw milk and cow-shares was legal in Washington state, however, Washington farms that provide raw milk were required to be licensed and meet milk production and processing standards, and pass sanitation inspections. This farm was not licensed and had sanitation problems.