Dendrochronological responses to an eruption of Mount Hood, Oregon, including new dendrochemical evidence, are documented here. Mount Hood, a stratovolcano of the Cascade Volcanic Arc (Fig. 1a), is thought to have erupted in AD 1781, as determined from tree death dates (Pringle et al. 2008), ring-width reductions (Sheppard et al., 2008a), and historical documents (Cameron and Pringle 1986, 1987). Ring-width evidence alone can indicate past volcanic eruptions (Yamaguchi and Lawrence 1993), but elemental concentrations in tree rings also reflect environmental changes brought about by eruptions (Hughes 1988). Dendrochemistry has been useful in past research of eruptions (Pearson et al. 2005; Sheppard et al., 2008b), so it was tried on Mount Hood and its 1781 eruption.