The language described in this monograph is spoken by a small hilltribe in Northern Indochina. Its existence has attracted considerable attention because of the legendary and intriguing primitiveness of the Mlabri or 'Spirits of the Yellow Leaves', as they are traditionally called, but reliable information about the cultural heritage and particularly the language is sparse. This is true in particular of an ethnic subgroup whose culture and language are now close to extinction: the group is referred to as the 'Minor Mlabri'. This monograph is based on field notes from 1988 and later years in which the author visited the 'Minor-Mlabri'. The Mlabri are traditionally hunter-gatherers and seem to have been so for a long time. Until recently this was more or less the lifestyle of the small group under study here. They now associate with Hmongs in remote villages because they were for several years trapped in the war zone between Laos and Thailand and the few survivors of the 'Minor-Mlabri' had to settle down in safer environments. Deforestation has made it increasingly difficult for them to live their traditional life in the area where they belong. Up to now, the Mlabri language (in all its varieties) has been unknown.