Abstract
The Abberrant Behaviour Checklist was administered to 209 British mentally handicapped adults in two large residential facilities. This sample induced a substantial proportion (45%) of non-ambulant people not included in previous studies. The five-factor solution originally reported by Aman et al. (1985a) was replicated using both four-point ratings and dichotomously recorded rating. For both methods of scoring, the five scales derived from Aman et al.''s original factor analysis remained highly internally consistent. Dichotomously coded ratings may offer the advantage over four-point ratings of retaining the same factor structure with better reliability.