Abstract: A flexible tube filled with a liquid core material for transmitting, by total internal reflections within the tube, laser energy at relatively high power levels from a laser to a desired area of application. The tube and liquid materials are selected to be transparent to light at the wave length of output from the laser, and such that the tube material has a refractive index substantially lower than that of the liquid core material. Also disclosed are a number of liquid materials having highly desirable properties of low toxicity, color stability, low volatility, and compressibility. Various sealing means and input and output windows are disclosed for use at the ends of the tube.