The nucleation of diamond films could be greatly enhanced on mirror-polished Si substrate by a pulsed Nd:YAG laser beam without any thermal- and plasma-assisted processes during a very short time. The nucleation density increased with decreasing laser power density from 1.38 x 10(10) to 1.17 x 10(9) W/cm(2) and deposition pressure from 1013 to 4 mbar. The pulsed laser beam made no contribution to enhance nucleation at substrate temperature as low as 650 degreesC. X-ray diffraction measurements showed the (1 1 1) diffraction peak of diamond for the samples obtained using only pulsed laser during 40 min. The enhanced nucleation and growth of diamond crystallites were attributed to effective excitation of reactive gases and etching of non-diamond carbon phases by the pulsed laser beam.