Randomised controlled trials and systematic reviews would be the golden standard for therapeutical studies; unfortunately they are really few in this field. It is anyway significative that all the studies reported focus on the use of antipsychotics in people with intellectual disability presenting behavioural problems. To increase the validity of these studies it is recommendable to proceed only with well-designed studies, possibly double-blind versus placebo or other medications. There is need to define precise inclusion criteria, precise symptomatological or behavioural targets and adaptative ability assessment, using valid and reliable diagnostic instruments.