Purpose: The objectives of the present investigation were to study fluoride (F) release from NaF-impregnated chewing sticks (Miswaks) in vitro and to study the F clearance in saliva and the F oral retention in vivo. Materials and Methods: Both fresh and old Miswaks were collected from 10 stores in Saudi Arabia and fluoridated in 0.01%, 0.1%, 0.5%, 1% and 3% NaF. The F release was studied in vitro up to 60 min. In vivo, 10 subjects used Miswaks fluoridated in 0.01%, 0.1%, 0.5%, 1% and 3% NaF for 2 min (Series I). The subjects were asked to spit out all saliva in a beaker during a 12-min period without swallowing. The F present in the obtained saliva was considered to represent the 'F retention'. In Series II, the same type of Miswaks were used as in Series I. Repeated whole saliva unstimulated samples were collected before and up to 30 min after. These two series were carried out in another 10 subjects (Series III and IV), but with Miswaks fluoridated in a more narrow range of concentration (0.05% to 0.5% NaF). Brushing with 1 g of F-containing dentifrice (0.32% NaF) was used as a control. Results: There were only small differences between fresh and old Miswaks, but great variations were observed between Miswaks that were purchased from different stores. Miswaks fluoridated in 0.1% to 0.5% NaF could be considered as an 'optimum level' with respect to both the F concentration in saliva and the F retention. Conclusions: It is recommended to use fresh Miswaks impregnated in 0.1% NaF or a maximum of 0.5% NaF for a day, as they are interesting and safe products for the prevention of caries and could be widely used in countries such as Saudi Arabia. Keywords: chewing stick, fluoride, fluoride retention, impregnation, Miswak, saliva, Salvadora persica