Abstract: With the potential advent of genetically modified herbicide-resistant (GMHR) crops inthe EU, changes in patterns of herbicide use are predicted. Broad-spectrum, non-selectiveherbicides used with GMHR crops are expected to substitute for a set of currently usedherbicides, which might alter the agro-environmental footprint from crop production. To test thishypothesis, the environmental impact of various herbicide regimes currently used with non-GMHR maize in Belgium was calculated and compared with that of possible herbicide regimesapplied in GMHR maize. Impacts on human health and the environment were calculated via thepesticide occupational and environmental risk (POCER) indicator. Results showed that theenvironmental impact of herbicide regimes solely relying on the active ingredients glyphosate(GLY) or glufosinate-ammonium (GLU) is lower than that of herbicide regimes used in non-GMHR maize. This beneficial environmental impact is reduced or counterbalanced dependingupon the use of other herbicides in association with GLY or GLU in GMHR maize.