With increasing age elastic fibres in human skin are progressively lysed and skin elasticity is also decreasing. Still there is an age-dependent increase of elastic fibre surface density, mostly due to an alteration of the fibres. The present experiments were undertaken to explore if L-fucose and fucose-rich polysaccharides (FROP-s) could influence elastin biosynthesis. We show here, that topical application of a fucose-containing preparation to the skin of hairless rats increased after 4 weeks the elastic fibre surface density by about 40%, shown by quantitative morphology. Using human skin fibroblasts in explant cultures, the addition of L-fucose or of FROP-3 increased the biosynthesis of immunoprecipitable tropoelastin by about 40%. No increase was found however of desmosine-isodesmosine in skin explant cultures after 72 h of incubation. The effect of L-fucose and FROP-3 on the biosynthesis of collagen and non-collagen proteins excreted by the skin explant cultures was also investigated. L-fucose, but not FROP-3, decreased collagen biosynthesis but both increased non-collagen protein biosynthesis. These results show that L-fucose and FROP-3 stimulate tropoelastin biosynthesis in vitro, and elastic fibre formation in vivo. This stimulation concerns also several non-collagen proteins secreted by skin explant cultures. Elastic fibre formation necessitates the simultaneous synthesis of several microfibrillar glycoproteins as well as of tropoelastin. The increased elastic fibre density in the in vivo experiments suggests that this is indeed achieved by L-fucose and FROP-3, further demonstrating their efficiency in the control of age-dependent modifications of connective tissues in general and of skin in particular.