  Lyman alpha emission presents a means of identifying very high redshift
galaxies, provided such objects can be reliably distinguished from foreground
emission-line galaxies. Here we report on a program of imaging and
spectroscopic studies being conducted with the Keck telescope, in concert with
additional efforts from the ground and with HST, to study such high-redshift
objects over the range from z=3 to 7. The first deep narrow-band imaging
studies with Keck are used to show that strong Lyman alpha emitters, such as
have been seen in high-redshift quasar fields at z>4.5, can be found in the
field populations. Based on studies of the HDF and the Hawaii Survey Fields
these are significant contributors to the star formation rates at these epochs.
