Aspen (Populus tremuloides Michx.) is highly genetically variable and is clonal. These properties make aspen an excellent model system for exploring the effects of intraspecific genetic variation on herbivores. We tested the hypothesis that aspen genetic variation across a large geographic scale can affect herbivores. We examined 17 aspen clones at three sites in north central Utah and 12 clones from south central Wisconsin growing in a common garden for insect herbivore populations. On three branches of four trees from each clone we examined leaves for sawfly (Phyllocolpa sp.) leaf galls and leaf rolls from an unknown species of lepidopteran. Additional leaves were collected for condensed tannin and phenolic glycoside analysis. We calculated the percentage of leaves that were galled or rolled and compared frequencies of leaf rollers and sawfly galls among clones in Utah and Wisconsin, and among sites in Utah. The frequency of leaves galled by sawflies (P=0.01) and rolled (P=0.0001) were significantly different among clones from both Utah and Wisconsin. Frequency of leaf rollers differed across Utah sites (P=0.001). Frequency of Phyllocolpa sp. leaf galls were not different among the three Utah sites but varied among clones in both states. For trees growing in a common garden in Wisconsin, frequency of sawflies is negatively correlated with phenolic glycoside concentrations (P <0.04), but positively correlated with tannin concentrations (P=0.009). We conclude that intraspecific genetic variation affects herbivore abundance, that the pattern is consistent across a geographic range of aspen, and that phytochemistry is a mechanism that explains these patterns.