Therefore, to investigate the effect of a national f-Hb-based CRC screening programme on population CRC-specific mortality and to assess if any effects are associated with sex and differ between men and women, we examined the CRC mortality rates in both women and men and in different age ranges, stratified by sex and age-group, during the decade before, and then since, the introduction of f-Hb screening in Scotland. Here, GSTM1 is linked to colorectal carcinoma.