The mutagenicity of arylboronic acids has recently become an important area of research because of their potential to be genotoxic impurities in active pharmaceutical ingredients. There is no known mechanism, so currently all structure-activity relationships have been derived using Ames test data. We present preliminary data supporting a hypothesis that the mutagenicity of arylboronic acids is related to the (11)B NMR chemical shift. This could indicate that the mutagenic activity of the arylboronic acids is related to the reactivity of the boron center.