Introduction. - The elderly represent the fastest growing population group in France. The care management of people suffering from dementia has become an important problem. Demented patients manifest behavioral problems, depression, apathy, impairment in social activities and Language skill disorders. The literature contains few studies investigating animal-assisted therapy for demented patients. However, there is a clear need for psychological assistance for this population. In the management of such behavioural. problems associated with dementia, we propose to develop a dog-assisted therapy. Three qualitative case studies are analysed to specify the perceptions of the therapist regarding animal-assisted therapy. Subjects and methodology. - This study is a qualitative pilot study. Subjects were two female and one mate patients admitted in a nursing home. They were diagnosed with severe dementia. Their mean age was 94 years. All of them agreed to attend the dog therapy activities and informed consent from their family was requested. We met these patients 15 times over nine months. The meetings always took place in the same place for 30 min, once a week. The evaluation was based on the clinical observations of the psychologist. Results. - This study revealed many psychological benefits for patients with dementia. The animal-assisted therapy had a calming effect on the patients. It could well be helpful as a communication link during therapy sessions. The dog, because of its unconditional acceptance, increases the self-esteem of the patient and contributes to a more secure environment. The patients, who rarely interacted socially, increased their interactions with the dog. In spite of the tack of normal verbal use of language, nonverbal communication continues including touching and posture. Furthermore, patients verbalized that the dog was affectionate and they could identify themselves with it. Conclusions. - This prospective study leads up to the conclusion that pet therapy could prove to be efficient. We conducted animal-assisted therapy sessions for patients with severe dementia and found that psychological assistance could be flexible enough, to meet the special needs of institutionalized persons suffering from dementia. The pet therapy programs may provide help for many patients, but the framework and conditions of this practice should be clearly defined, until the dog itself, can become the therapist. (C) L'Encephale, Paris, 2008.