A copolymer of polycarbosilane and perhydropolysilazane was obtained by reacting polycarbosilane with titanium n-butoxide and perhydropolysilazane. Titanium n-butoxide and perhydropolysilazane were essential for the polymer to show a thermosetting property. The thermosetting copolymers were converted into silicon carbide-based ceramics by pyrolysis in a stream of nitrogen to 1000 degrees C with about 80 wt% ceramic yield. The main phase of the pyrolysis product at 1500 degrees C in nitrogen was small crystallite beta-SiC. Elemental carbon, based on rule-of-mixtures composition, in the final ceramics could be reduced by varying the ratio of polycarbosilane/perhydropolysilazane. The copolymer was dry spun a nd pyrolysed to produce ceramic fibre. Pyrolysis in nitrogen to 1500 degrees C yielded a silicon carbide-based fibre with low oxygen and low elemental carbon content. A tensile strength of 1.8 GPa and an elastic modulus of 220 GPa were obtained for the fibre which ranged from 10-12 mu m in diameter. Crystallization to alpha-Si3N4, beta-SiC, and beta-Si3N4 proceeded on annealing in nitrogen at 1700 degrees C for 1 h.