Young stellar populations at high Z: Where are they?

Our view on the deep universe is strongly biassed towards the starlight tha t directly escapes from high-redshift galaxies, since we know very little o n the fraction of luminosity absorbed by dust. Attempts to correct for this effect directly from the slope of the UV spectra seem to suggest that a si gnificant fraction of the UV flux is extinguished. New constraints are now set on the fraction of dust-enshrouded young stellar populations by the det ection of the Cosmic Infrared Background, and faint galaxy counts at IR and submm wavelengths. We briefly review the observations and use a semi-analy tic model of galaxy formation and evolution to predict number counts consis tent with the background.