The relationship between density of elm leaf beetle,Xanthogaleruca luteola(Müller), and damage to English elm,Ulmus proceraSalisbury, and Siberian elm,Ulmus pumilaL., was studied in seven northern California cities in 1986 and 1987. Peak first-generation elm leaf beetle egg or larval densities were good predictors of cumulative foliage damage to English elm and to a lesser extent predicted Siberian elm damage. Egg density on both hosts was highly associated with the proportion of samples infested with eggs. The maximum proportion of presence-absence samples infested with first generation eggs predicted cumulative damage to English but not to Siberian elm. When no effort was made to control beetle populations most English elm trees sustained more than 40% damage to retained foliage, whereas damage to most Siberian elms was less.