An experimental investigation was made of parametric generation of ultrashort light pulses in KDP and ADP crystals pumped with the third and fourth harmonics of single picosecond pulses emitted from a YAG:Nd**3** plus laser. The frequency width of the parametric superluminescence ranged from 10 to 5300 cm** minus **1 depending on the phase conditions in the three-frequency interaction and the focusing parameters of the pump radiation. The efficiency of conversion of the pump radiation reached 10-15%. The results demonstrated potential usefulness of the parametric superluminescence continuum in picosecond spectroscopy.