We present initial results of a new , systematic search for massive star-formation in the host galaxies of the most luminous and probably most massive z \ga 4 radio-quiet quasars ( M _ { B } \leq - 27.5 ; \nu L _ { \nu } ( 1450 \AA ) > 10 ^ { 13 } \thinspace L _ { \odot } ) .
The survey , undertaken at 850 \mu m using SCUBA at the James Clerk Maxwell Telescope ( JCMT ) , has a target sensitivity limit of 3 \sigma \sim 10mJy , set to identify sources suitable for detailed follow-up e.g .
continuum mapping and molecular line diagnostics .
A total of 38 a z \ga 4 radio-quiet quasars have been observed at 850 \mu m , of which 8 a were detected ( > 3 \sigma ) with S _ { 850 \mu m } \ga 10 mJy ( submillimetre-loud ) .
The new detections almost triple the number of optically selected , submillimetre-loud z \ga 4 radio-quiet quasars known to date .
We include a detailed description of how our quasar sample is defined in terms of radio and optical properties .
As a by-product of our selection procedure we have identified 17 radio-loud quasars with z \ga 4 .

There is no strong evidence for trends in either detectability or 850 \mu m flux with absolute magnitude , M _ { B } .
We find that the weighted mean flux of the undetected sources is 2.0 \pm 0.6 mJy , consistent with an earlier estimate of \sim 3 mJy based on more sensitive observations of a sample z \ga 4 radio-quiet quasars ( McMahon et al . ,1999 ) .
This corresponds to an inferred starformation rate of \sim 1000 \hbox { $ \thinspace M _ { \odot } $ } { \thinspace yr } ^ { -1 } , similar to Arp220 .
The typical starformation timescale for the submillimetre-bright sources is \sim 1 { \thinspace Gyr } , 10 times longer than the typical accretion-driven e-folding timescale of \sim 5 \times 10 ^ { 7 } years .
Our 850 \mu m detection of the z = 4.4 quasar PSS J1048 + 4407 when analysed in conjunction with 1.2mm single-dish and interferometric observations suggests that this source is resolved on angular scales of 1-2″ ( 6-12 kpc ) .
In addition , we present a new optical spectrum of this source , identifying it as a broad absorption line ( BAL ) quasar .
The new redshift is outside that covered in a recent CO line search by Guilloteau et al . , ( 1999 ) , highlighting the need for accurate redshifts for the obervation and interpretation of high-redshift line studies .