The parameters of a laser which govern stone fragmentation are the pulse duration, wavelength and fibre diameter. The pulse duration is the most important parameter governing fibre transmission. The shorter the pulse duration the less tissue damage and the easier the plasma production at the stone surface but the greater the difficulty to transmit the laser energy through the fibre. At 1 microsecond pulse duration the laser wavelength is highly significant because it governs the degree of absorption at the stone surface necessary for plasma production. Transmission of this laser energy through 200 micron core fibres is straightforward. Fragmentation is achieved by placing the fibre in contact with the stone surface. There is negligible tissue injury. A miniaturised ureteroscope has been developed specifically for the laser. This appears to be easier to use and carries less risk of instrumentational injury to the ureter.