A process for producing boron nitride nanotubes and nanotube films, which process comprises heating a liquid composition comprising boron particles and a metal compound, wherein heating takes place at a temperature of from 800-1300° C. in a gaseous atmosphere containing nitrogen that causes boron nitride nanotubes to grow, and wherein the boron particles have an average particle size of less than 100 nm, and wherein the metal compound is selected such that it promotes the growth of boron nitride nanotubes during heating.