Si nanowires with uniform size have been synthesized by laser ablation of highly pure Si powder targets mixed withSiO2.A bulk quantity of Si nanowires was successfully obtained by mixing 30&percent;–70&percent; ofSiO2into the Si powder target.SiO2played a crucial role in enhancing the formation and growth of the Si nanowires. The morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy. No evidence of metal was found at the tips. The results suggest that Si oxide is more important than metal in catalyzing the formation of Si nanowires. ©1998 American Institute of Physics.