Origins of the principal lines of Rattus norvegicus used in behavior genetic research are identified. Broad descriptions are provided for 15 of the Har strains and substrains of well-established inbred lines and behaviorally selected stocks. Marker genes are identified for coat and major histocompatibility complex (MHC) loci. Detailed characteristics are summarized for 12 of these lines using a comprehensive behavioral test battery composed of a variety of measures of expressive behavior, learning, and physiological characteristics.