Summary form only given. CsLiB/sub 6/O/sub 10/ (CLBO) is a new nonlinear material, which has been used successfully for harmonic generation of nanosecond laser pulses with repetition rates from 10 Hz to 1 kHz. In the investigations reported in the paper CLBO is used as nonlinear crystal in a ps optical parametric oscillator (OPO), which is synchronously pumped by the fourth harmonic (266 nm) of a CW mode-locked diode-pumped Nd:YVO/sub 4/ laser. This OPO is, to our best knowledge, the first 266 nm pumped CW mode-locked OPO. One of the most interesting features of this OPO is the generation of blue signal and red idler radiation, which was tunable in the spectral regions of 442-480 nm and 597-668 nm, respectively.