This paper aims to examine the knowledge of local medicinal plants among independent Tibetan doctors from lower Mustang District in Nepal. It particularly focuses on plant identification, classification, criteria of attribution of curative properties, and use. Tibetan materia medica is presented from the local perspective. The fieldwork was conducted in July-August 2001. This research employed fine-grained qualitative documentation and analysis of specific learned Tibetan doctors. The methodology was based on ethnographic research techniques primarily including participant observation, open conversations, and studies of medical texts. The three informants are the most renowned Tibetan medical practitioners of the area. The author participated in the collection of medicinal plants and medical activities at local clinics, and collected and identified seventy-five medicinal agents. Field data confirm that variability in concept of materia medica is an important feature of Tibetan medicine, and notably among independent medical practitioners from high Himalayan valleys. This disparity is mainly determined by local ecological setting, how remote a region is, economic, social, and historical issues. The three informants from Lower Mustang have their own specific ways of selecting, identifying, categorizing, and using medicinal agents, which may differ from the ones of practitioners from adjacent regions, and particularly from so-called "standard Tibetan medicine", expounded in the Four Tantras and its main commentaries.