Natural fibers are very important and very useful fibers which compete and coexist together with man-made fibers especially in area of quality, sustainability and economy of their production. In this paper we present the level of production (35-40 million tons/year) contra man made fibres and special treatment of them like enzymatic, liquid ammonia, plasma, corona, and ultra sound. Natural fibres are characterised by air permeability, hygroscopicity and capability of giving up moisture, no release of substances harmful for health, no allergic effect, biodegrability and safer behaviour in fire conditions in comparison to man-made fibers. Natural fibers conduct heat, can be dyed well, resist mildew and have natural antibacterial properties, block UV and are easy to make them flame retardant. Genetic modification of lignocellulosic fibrous raw materials improve their performance and giving possibilites to obtain polyhydroxy-alcanate (PHA) "in statu nascendi" in plant. For this reason, United Nations and FAO declared the year 2009 the International Year of Natural Fibres. In the 21st century there is a growing awareness about the future of renewable, sustainable and biodegradable fibrous materials.