The Western Regional Coordinating Committee No. 66 (WRCC-66) facilitated the development in cultivated cereals of host plant resistance to the Russian wheat aphid, Diuraphis noxia (Mordvilko), a widespread pest of cereals in the western United States for which genetic resistance was not readily available. WRCC-66 supported host plant resistance development by exchange of evaluation methodologies, coordination of cereals collections evaluations, rapidly distributing breeding materials, and coordinating regional evaluation of new resistance sources. Groups participating in WRCC-66 have evaluated >25,000 strains (accessions) of small grains in wheat. Triticum aestivum L. and T. turgidum var. durum L., barley. Hordeum vulgare L., and related cereal species. Eighty-six reproducible host plant resistance sources for D. noxia resistance are referenced in this review. Most of the resistance sources have combined mechanisms of resistance with antibiosis and tolerance the most common combination. The least common mechanism of resistance was antixenosis, singularly or in combination with tolerance. Six genes (Dn1–6) conferring resistance have been documented in wheat, 2 genes in barley, and 1 gene in triticale, X Triticosecale Witmack. Additional genes are likely to exist in these 3 species. Breeding efforts have identified improved cultivars of barley (S8, S13) and improved triticales (‘Brumby’ and ‘Eronga 83’) with good host plant resistance levels. Improved host plant resistance germplasm of wheat (CORWA1, 9 sibs of P1 372129/2 * Pondera, KS92WRGC24, KS92WRGC25, STARS 9302W, and STARS 9303W) and barley (STARS 9301W) have been selected and released by programs participating in WRCC-66. In 1994, Colorado released the D. noxia-resistant wheat cultivar ‘Halt’, that carries the Dn4 gene from P1 372129. The broad range of resistance sources available may preclude significant economic loss should biotypes develop. Future research directions should emphasize integration of host plant resistance with biological control of D. noxia and crop managment strategies.