Background Randomized controlled trials evaluating biological therapy have shown improvements in survival from metastatic colorectal cancer (mCRC). Subjects in the trials represent a selected proportion of mCRC patients. We have the potential to assess the impact of biological therapy on mCRC outcomes, particularly the effect of bevacizumab, from a population-based clinical registry by comparing two time cohorts with differences in therapy accessibility. Material and methods A retrospective cohort study was performed by analyzing the South Australian (SA) mCRC registry data based on diagnosis in two time periods: