Colorectal cancer (CRC) has the second highest cancer prevalence and mortality rates in Australia. The Australian National Bowel Cancer Screening Program (NBCSP) aims to increase early detection of CRC by offering free faecal occult blood testing. The NBCSP aims to offer choice to consumers about whether or not to participate in screening. This article presents data on trust, choice and perceived obligation to participate in the NBCSP by population groups with low uptake. A qualitative study was undertaken in South Australia. We interviewed 94 people from four culturally distinct groups: Greek, Iranian, Anglo-Australian and Indigenous peoples. This article demonstrates the complexity of factors shaping the choice, or lack thereof, to participate in the NBCSP. Informed choice is based on adequate knowledge, although this varied among our participants, highlighting the need for more health education in appropriate languages. An obligation to participate was found in the Iranian and Anglo-Australian groups and resulted from an established personal relationship with the doctor, a sense of duty, the acknowledgement of government investment and appreciation. Overall, this article makes a link between trust, choice and obligation, adding to literature on the sociology of trust and medical screening and highlighting important issues in the need of a policy and practice to improve CRC screening rates.