  We review the spectral properties of the population of star forming galaxies
at z = 3 discovered using a colour selection technique which targets the Lyman
discontinuity at 912 Angstroms. The UV luminosity of the typical z = 3 galaxy
exceeds by more than one order of magnitude that of the most luminous
starbursts in the nearby universe, although the maximum star formation
intensity (SFR per unit area) is within the limits found in local surveys. We
consider in detail the likely magnitude of dust extinction and conclude that
published estimates of the volume-averaged star formation rate at high z need
to be revised to higher values by a factor of about 3. This correction improves
the agreement between the observations and recent theoretical predictions.
Lyman alpha emission is generally weak, most likely as a result of resonant
scattering. The large equivalent widths of the strongest interstellar lines and
their systematic blueshift (by up to several hundred km/s) relative to the
Lyman alpha emission line are indicative of highly energetic outflows in the
interstellar medium. Pilot observations have detected the redshifted Hbeta and
[O III] emission lines in the K band. The widths of these features imply
dynamical masses of approximately 10^{10} solar masses for the innermost star
forming regions; the total masses involved are likely to exceed 10^{12} solar
masses.
