Abstract: A system for welding tissue by irradiation with laser energy, includes a laser for generating a beam of laser energy and directing the beam toward the tissue so as to irradiate the region to be welded. The laser has a control input and is responsive to a control signal supplied to said control input to adjust the power of the beam of laser energy. An infrared sensor senses the temperature of the tissue in the region to be welded by sensing infrared radiation coming from this region. The sensor provides a sensor output indicative of the temperature. A computer control arrangement is responsive to the sensor output. The computer control arrangement supplies a control signal to said laser such that the region to be welded is heated to a predetermined temperature.