Macroscopic and microscopic complete resection, i.e. R0 resection, is a basic principle oncologic hepatopancreatobiliary (HPB) surgery. The reported R I rates for different HPB tumor entities vary considerably, most likely because of ambiguities in the exact definition of R1 resection and the lack of standardized histopathologic examination and reporting. R1 resections can be interpreted as technical/surgical failure (e.g. for small, peripherally located liver tumors). In most cases, however, R1 resections are determined by the anatomic location of the tumor and the growth pattern (e.g. pancreatic cancer with perineural invasion). R0 resections have been identified as positive predictive markers for several HPB tumors (in comparison to R1 resection). Therefore HPB surgeons should always aim at macroscopic and microscopic complete resections. Nonetheless, R1 resections often provide an advantage over no resection with respect to survival and quality of life in patients with these tumors.