The efficiency of second-harmonic generation and the degree of compression of picosecond pulses from a neodymium–glass laser were enhanced by a delay between the ordinary and extraordinary pulses interacting in KDP crystals. The conversion efficiency was increased by a factor of 1.5 (from 33% to 50%) and the second-harmonic pulses were compressed by a factor of 2.4 (from 4.8 to 2 ps).