Mecinus janthinus (Coleoptera: Curculionidae) is a stem boring weevil that has been introduced as a biological control agent for Dalmatian toadflax (Linaria genistifolia (L.) P. Mill subsp. dalmatica). I examined the impact of host-plant water stress on oviposition rates, beetle survivorship and adult size. Beetles were caged on potted toadflax plants and given the choice between well watered and drought stressed plants. There was no indication that adults prefered either drought stressed or well-watered plants for oviposition (mean ± SE) number of weevils per stem=29.0 ± 6.135 for well-watered plants and 24.56 ± 6.135 for drought stressed plants). However, in response to the low water treatment M. janthinus survivorship was significantly reduced. In the well-watered treatment 60% of eggs deposited survived to adulthood, in contrast to only 40% in the low water treatment.