OBJECTIVE: The National Bowel Cancer Screening Program (NBCSP) is a population-based screening program based on a mailed screening invitation and immunochemical faecal occult blood test. Initial published evidence from the NBCSP concurs with international evidence on similar colorectal cancer screening programs about the unequal participation by different population sub-groups. The aim of the paper is to present an analysis of the equity of the NBCSP for South Australia, using the concept of horizontal equity, in order to identify geographical areas and population groups which may benefit from targeted approaches to increase participation rates in colorectal cancer screening. METHOD: De-identified data from the NBCSP (February 2007 to July 2008) were provided by Medicare Australia. Univariate and multivariate statistical analyses were undertaken in order to identify the predictors of participation rates in the NBCSP. RESULTS: The overall participation rate was 46.1%, although this was statistically significantly different (p<0.001) by gender (42.6% for males and 49.5% for females), socioeconomic status (40% in most deprived quintile through to 48.1% in most affluent quintile) and remoteness (45.6% for metropolitan, 46% for remote and 48.6% for rural areas). These findings were confirmed in multivariate analyses. Of the NBCSP participants, 0.24% (CI 95% 0.20-0.30) identified themselves as Indigenous and 8% (CI 95% 7.7-8.3) reported speaking a language other than English at home. CONCLUSION: Findings from this study suggest inequities in participation in the NBCSP on the basis of gender, geographical location, Indigenous status and language spoken at home.