The study was conducted around Debre Libanos monastery from October 2005 to June 2006. A total of 250 villagers, 13 monks and 3 nuns were interviewed using semistructured questionnaire on the knowledge and use of medicinal plants. The informant consensus factor (ICF) and the fidelity level (FL) of the species were determined. Eighty medicinal plant species were reported. The average medicinal plant reported by a female is 1.67+/-0.33 and a male is 5.77+/-0.71 with significant difference between them (alpha=0.05, p=0.023). The ICF values demonstrated that local people tend to agree more with each other in terms of the plants used to treat 'Mich' and headache (0.69) and intestinal illness and parasites (0.68) but a much more diverse group of plants are cited to treat problems related to rabies (0.14) and unidentified swelling and cancer (0.11). The FL values are also similar to ICF values. The knowledge of the villagers close to the monastery is found to be higher than those distant from the monastery and the correlation between Abichu and Telaye (r=0.970, alpha=0.05, p=0.001), and Zegamel and Doreni (r=0.745, alpha=0.05, p=0.027) is significant indicating the relationships between the number of plants reported by the informants and the distance from the monasteries to the villages. This study was not able to determine the knowledge difference between the villagers and the monastery dwellers because the monks and nuns were not willing to give information on the knowledge and use of medicinal plants. This may result in the long run in loss of local knowledge in the surrounding area and the country at large for preparation of pharmacologically effective remedies.