Because of its potential impact on maize, rapid detection and diagnosis of brown stripe downy mildew is essential. The National Plant Diagnostic Network (NPDN) has established protocols for recognition of Select Agents for participating laboratories. Due to the potential impact of an introduction of brown stripe downy mildew, this information is being widely disseminated so that suspect samples can be quickly and correctly identified. Accepted for publication 10 July 2007. Published 8 November 2007.