Modified (sculpted) optical fiber tips for medical delivery systems are described. Tips have aspherical profiles (parabolic, hyperbolic, etc.) Light distributions of modified silica (n = 1.457) tips were calculated using a 3-D ray-tracing program in air and water. It was found that the focusing effects of aspherical tips are from 2.5 to 3.0 times better than those of spherical tips. It is possible to increase the irradiance of tissue in water by about 6 to 9 times using normal silica fiber with high efficiency (without total internal reflection). Experiments were performed in air and water, using registration of light distribution with a CCD-camera, and confirmed the theoretical predictions.