Sizal fibre (length 2-5 mm and diam. 4-10 mu m) were used as a filler 1 to 7,5% by mass for polyurethane elastomers. The fibres were added to the urethane pre-polymers synthesized of diphenyl methane diisocynate and polyester polyol Poles55/20. As a chain extender, butylene glycol was used. The reaction was catalyzed with 1,4-diazobicyclo[2.2.2]octane. The PU samples were heated at 110 degrees C for 6 or 24 h. The elastomers heated for 24 h showed higher tensile strength and Schob elasticity than those heated for 6 h.