Aim  The aim of the study was to apply an intervention to the area of sexual knowledge in order to determine if capacity to make sexuality‐related decisions could be improved.

Method  The study adopted a single subject design using multiple baseline method with four adults with a moderate intellectual disability. The intervention consisted of individually tailored sex education adapted from Living Your Life (Bustard 2003). Treatment was offered to each participant twice weekly for a 10‐week period on a one‐to‐one basis. The Sexual Consent and Education Assessment (SCEA, Kennedy 1993) was used for measurement purposes. The SCEA K‐Scale (knowledge) and the S‐Scale (safety practices) were administered weekly throughout the baseline, treatment and post‐treatment phases of the study. Staff concerns were also assessed using the SCEA Inappropriate Sexual Behaviour Scale.

Results  All four participants improved their decision‐making capacity in all targeted areas as measured by improvements in K‐Scale and S‐Scale scores. Staff concerns were not increased as indicated by results on the Inappropriate Sexual Behaviour Scale. Six‐month follow‐up data for three of the participants showed maintenance of scores on the S‐Scale and some decay in scores on the K‐Scale from post‐intervention performance.

Conclusion  The results demonstrate that tailored sexuality education can improve capacity to make sexuality‐related decisions.