A fumigation experiment was performed in which six plant species representing the European flora were exposed to a range of DBP concentrations. Controlled amounts of DBP-saturated air were injected into the ingoing air-streams of plant fumigation chambers, maintaining constant concentrations there for a period of up to 76 days. The target concentrations were a control, 0.8, 1.5, 3.5, and 10.0 µg m-3. The variation in sensitivity between plant species to atmospheric DBP was quantified on the basis of whole plant biomass in order to derive no-observed-effect-concentrations (NOECs). Significant dose–response relationships, based on realised concentrations, were thus derived using non-linear regression, resulting in NOECs of 0.51 µg m-3 for Trifolium repens, 0.96 µg m-3 for Brassica campestris, 1.87 µg m-3 for Phaseolus vulgaris and 2.21 µg m-3 for Plantago major. A significant effect was also observed for Holcus lanatus at 12.4 µg m-3 DBP, but due to the variation at lower levels of DBP exposure, no dose–response relationship could be derived. No significant effect on growth of current year needles in Picea abies was observed, even at the highest level of DBP, 13.7 µg m-3. Based on statistical extrapolation according to Aldenberg and Slob [Ecotox. Environ. Safety, 25 (1993) 48], an overall predicted no-effect concentration (PNEC) for the plant-atmosphere compartment of 0.33 µg m-3 DBP was calculated. The PNEC was calculated using the mean and standard deviation of the NOEC for four of the tested species and an extrapolation factor. In addition to changes in leaf colour, leaf crinkling and growth reduction, a number of not quantified observations are described, indicating that DBP affects the physiology as well as the morphology of these species.