The term “natural fibers” covers a broad range of vegetable, animal, and mineral fibers. However, in the composites industry, it usually refers to wood fiber and plant-based bast, leaf, seed, and stem fibers. These fibers often contribute greatly to the structural performance of the plant and, when used in plastic composites, can provide significant reinforcement. Below is a brief introduction to some of the natural fibers used in plastics. More detailed information can be found elsewhere. Although natural fibers have been used in composites for many years, interest in these fibers has waned with the development of synthetic fibers such as glass and carbon fibers. However, recently there has been a resurgence of interest, largely because of ecological considerations, legislative directives, and technological advances. One of the largest areas of recent growth in natural fiber plastic composites is the automotive industry, particularly in Europe, where the low density of the natural fibers and increasing environmental pressures are giving natural fibers an advantage. Most of the composites currently made with natural fibers are press-molded although a wide range of processes have been investigated. Flax is the most used natural fiber (excluding wood) in the European automotive industry, most of which is obtained as a by-product of the textile industry . However, other natural fibers such as jute, kenaf, sisal, coir, hemp, and abaca are also used. Natural fibers are typically combined with polypropylene, polyester, or polyurethane to produce such components as door and trunk liners, parcel shelves, seat backs, interior sunroof shields, and headrests. European consumption of natural fibers in automotive composites was estimated at 26000 tons in 2003 and is expected to grow by 10% per year. Worldwide consumption in all applications by 2010 has been estimated at 110 000-120000 tons per annum in a variety of applications including automotive, building, appliances and business equipment, and consumer products.