Inflammation associated reactive oxygen and nitrogen species (RONs), including peroxynitrite (ONOO−) and nitric oxide (NO· ), create base lesions that potentially play a role in the toxicity and large-scale genomic rearrangements associated with many malignancies. Nevertheless, little is known about the functional role of base excision repair (BER) deficiencies following exposure to RONs. Here, we explore the role of XRCC1 in modulating the levels of RONs-induced genotoxicity. XRCC1 is a scaffold protein critical for BER for which polymorphisms modulate the risk of cancer. We exploited CHO and human glioblastoma cell lines engineered to carry varied levels of BER components to study XRCC1. Cytotoxicity and SSB-intermediate levels were evaluated following exposure to the ONOO− donor, SIN-1, and to gaseous NO·. XRCC1 null cells are slightly more sensitive to SIN-1 toxicity. To explore the potential importance of XRCC1 in response to NO· -induced lesions, we used small-scale bioreactors to expose cells to NO· and found that XRCC1 does not impact genotoxicity in CHO cells, suggesting a minimal role for XRCC1 in response to RONs. However, using a molecular beacon assay to measure AAG-mediated lesion removal in vitro, we found that XRCC1 facilitates AAG-initiated BER of two key NO· -induced lesions: 1,N6-ethenoadenine and hypoxanthine. Furthermore, overexpression of AAG rendered XRCC1 cells sensitive to NO· -induced DNA damage and toxicity. These results show that AAG is a key glycosylase in response to NO· exposure and that the cellular and functional impact of XRCC1 depends upon the level of AAG. These studies are some of the first to assess the functional role of XRCC1 in response to NO·, and demonstrate the importance of BER balance when considering the impact of XRCC1 polymorphisms in response to RONs.