  We present results from two surveys for radio-loud quasars. These are (1) a
northern survey reaching S(5GHz)=0.2Jy and (2) the Parkes QSO survey reaching
S(2.7GHz)=0.25Jy, which together cover most of the sky. Both surveys use
digitised plate material to identify the majority of the radio sources and CCD
images to identify the optically fainter sources. The northern survey was
targeted specifically at z > 3 QSOs and has produced more than 20, one of
which, at z=4.72, is the most distant radio source known. This sample is
identified to the POSS-I plate limit (20 mag) over an area of 3.7sr, or 12 000
sq deg. With the addition of CCD identifications, an effective sub area of 2400
sq degrees is 97% identified. In the South the Parkes QSO survey now has
complete redshift information for all 442 flat-spectrum quasars. These cover
the redshift range 0 < z < 4.5 and show a clear drop-off in space density at
redshifts above 3. The form of this decline is remarkably similar in form to
that seen in optically-selected samples of quasars. Since radio emission is
unaffected by dust this implies that dust has a minimal effect on the observed
drop-off seen in optical samples. Analysis of our radio-selected samples
suggests that the decline in space density at high redshift is more pronounced
for less powerful radio sources. We are planning a new survey that will be
sensitive to bright quasars with redshifts up to 6.
