A picosecond streak camera which operates at a repetition rate of 140 MHz in synchronism with a CW mode -locked laser is described. Experimental results are presented which indicate that the SYNCHROSCAN system at present has a temporal resolution nvlOpsec and the possibility of improving this resolution :lpsec is discussed. SYNCHROSCAN has been built into a commercially available camera (IMACON 675) and a temporal resolution <20psec demonstrated in this form.