Recent sub-mm observations (Smail, Ivison & Blain 1997; Hughes et al. 1998; Barger et al. 1998; Eales et al. 1998) have detected a population of dust-obscured, star-forming galaxies at high redshift. The star-formation density associated with this population is substantially higher than estimates based on optically-selected samples of distant galaxies, demonstrating the need for sub-mm observations to determine the total star-formation history of the Universe correctly.

In this talk, I'll report on the progress of deep sub-mm surveys with SCUBA and the intensive multi-waveband follow-up observations through which we hope to better understand the nature of the sub-mm galaxy population.