A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p &gt; 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p &lt; 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize.