This article describes a behavioural mental status assessment for developmentally disabled clients. Readers will learn the importance of distinguishing behaviours from co-morbid disorders, intellectual distortion, psychosocial masking & baseline exaggeration. A quick reference guide, “JOMAAC” (judgement, orientation, memory, affect, attitude & cognition) is provided to guide nurses through an assessment. All clients should be assessed for risk of suicide, elopement & danger to self or others.