The ethnobotanical and phytotherapeutic study conducted in Mvouandzi (4°10′00″ S, 13°25′00″ E), sub-prefecture of Kayes (Bouenza - Congo), is based on the floristic inventory, the personalized interviews and focus groups. The target population, aged between 15 to 70 years or more, is divided into 3 age groups, and consists of 46 informants (12 men and 34 women) who possess the plant secrets. The floristic inventory lists 60 useful species, corresponding to 53 genera and 35 families. The medicinal cohort is associated with 109 recipes and 57 diseases and symptoms. Classified as a sphere of diseases and symptoms, infectious and parasitic diseases predominate (27.11%) and retain 30.27% of recipes. All organs (vegetative and generative) intervene in the daily satisfaction of the needs of the populations. Ethno-sociological analysis reveals that the level of endogenous knowledge is proportional to the subjects' age and in this matter, women by virtue of their role as manager and guardian of morals, excel in the exploitation of empirical knowledge. Data on the value of ethnobotanical use, the informant consensus factor and the level of fidelity show that these plants are strongly involved in the primary care of this society. Notwithstanding the inseparable link between man and his environment, the value associated with this biodiversity, the socio-cultural foundation of the Kouni ethnic-linguistic community, is inevitably eroded. The reasons for this are the rural exodus, the main corollary of which is the ageing of the population, and the effects inherent in the construction of physical communication infrastructures.