The aim of this study is to determine the speech characteristics of 20 patients with Alzheimer's disease (AD) in comparison with those of 20 age, sex, and socio-economic matched healthy controls. The first research is designed to study temporal organization of speech in the context of normal and pathological cognitive aging, and in the evolution of Alzheimer dementia using five variables: Verbal Rate, Transformed Phonation Rate, Mean Duration of Pauses, Standardized Phonation Time, and Standardized Pause Rate. We investigated also the frequency and the duration of pauses and lengthening considered as dysfluencies. The results show that patient's discourse is marked by frequent silent pauses and lengthening. A decline of productivity, measured with verbal rate; low effectiveness of time of phonation, reflected by transformed phonation rate measure; and an increase number of pauses, measured with standardized pause rate were observed in the group of Alzheimer patients more affected than the group of patients at mild to moderate stage.