Ethnobotany links cultural and environmental factors with conceptions regarding plants and the uses that are made of them. A study was made in nine communities in the Arari region of the Itacoatiara municipality of Amazonas State, Brazil, using semi-structured interviews and participant observation to identify the medicinal plants, what they were used for and the age groups of holders of such knowledge. Holders of traditional knowledge were mostly women aged 55 or older (70 %). During the survey, 384 references were obtained, involving 105 species from 40 botanical families. Leaves were the most commonly used plant part, most commonly in the form of a tea. Illness symptoms were distinguished using the DATA-SUS classification. Stomach and throat ailments were the most cited. Plants were also used in the pursuit of mental well-being, as in combating the ´evil eye´. Some prominent species received ten or more references, and indices of Fidelity (0.8) and Order Significance (0.64) placing aloe (Aloe vera (L.) Burm. F.) in first place, followed by West Indian goosefoot (Chenopodium ambrosioides L.) (0.72 and 0.51) and mojito mint (Mentha villosa Huds) (0.66 and 0.43). Despite the existence of a large number of medicinal species and their widespread use among older people, few young people held medicinal plant knowledge. Some way of introducing traditional knowledge to this age group is needed.