There are few self-report measures of morality. The Religious Status Inventory—‘Being Ethical’ subscale represents one approach. However, at present there is limited information on the psychometric properties of either the original 20-item version (RSInv-20) or the shortened embedded 10-item version (RSInv-S10). The aim of the present study was to provide psychometric data on the internal reliability of these two versions of the ‘Being Ethical’ subscale. As part of a larger study, 595 Northern Irish adolescents, drawn from both Grammar and Secondary schools, completed the RSInv-20. An unsatisfactory level of internal reliability was found for the RSInv-20 (Cronbach’s alpha = 0.42), but a satisfactory level of internal reliability was found for the RSInv-S10 (Cronbach’s alpha = 0.70). Subsequent item analysis produced an alternative 10-item version (RSInv-A10) that provided the optimum level of internal reliability for a 10-item measure in the present sample (Cronbach’s alpha = 0.74). In addition, on all three versions of the measure (RSInv-20, RSInv-S10, and RSInv-A10), differences were found in levels of internal reliability among Grammar and Secondary school respondents, with the former producing higher levels of internal reliability.