Can laser light be used to trigger lightning? Previous attempts [1] have been unsuccessfull, because they created a dense plasma opaque to the beam by avalanche ionization with an intense infrared laser. The method under investigation here uses a fs UV pulse at 248 nm to create a moderate (1013/cm3) electron density in a narrow (a few cm in diameter) vertical column of air. The charges are injected in the high field region between ground and cloud (at least 100 m altitude). The motion of the charges in the “external” atmospheric field result in a field enhancement (up to tenfold) at the “tip” of the cylinder of charges. A long (up to 1 µs) visible laser pulse has to be sent simultaneously through the same path to prevent the creation of negative ions O− and O2−