The cultivation of Lepidoptera-resistant Bt-maize may affect non-target butterflies. We assessed the risk posed by event MON89034 x MON88017 (expressing Cry1A.105 and Cry2Ab2 against corn borers) to non-target Lepidoptera. Using the small tortoiseshell Aglais urticae, a butterfly species common in central Europe, as a test organism we (1) assessed the toxicity of Bt-maize pollen on butterfly larvae; (2) measured pollen deposition on leaves of the host plant Urtica dioica; (3) mapped the occurrence and distribution of host plants and larvae in two arable landscapes in Germany during maize anthesis; and (4) described the temporal occurrence of a one-year population of A. urticae. (1) Larvae fed 200 Bt-maize pollen grains/cm2 had a reduced feeding activity. Significant differences in developmental time existed at pollen densities of 300 Bt-maize pollen grains/cm2 and in survival at 400 grains/cm2. (2) The highest pollen amount found was 212 grains/cm2 at the field margin. Mean densities were much lower. (3) In one region over 50% of A. urticae nests were located within five metres of a maize field, while in the other all nests were found in more than 25 m distance to a maize field. (4) The percentage of larvae developing during maize anthesis was 19% in the study area. The amount of pollen from maize MON89034 x MON88017 found on host plants is unlikely to adversely affect a significant proportion of larvae of A. urticae. This paper concludes that the risk of event MON89034 x MON88017 to populations of this species is negligible.