The construction and development of a Belief in Human Benevolence scale (BHB), held to be useful for research into delinquent behaviour, was described. It was demonstrated to be reliable (α = 0.77) both with undergraduates and prisoners. Its validity is supported by correlations with theoretically related aspects of social cognition (interpreting relationships as cooperative and prison staff as treating prisoners fairly) and personality (oral pessimism and psychoticism). Its correlation with McGurk's measure of undercontrol suggests that it may distinguish between more and less delinquent offender personality types