  The Square Kilometre Array will be a revolutionary instrument for the study
of gas in the distant Universe. SKA1 will have sufficient sensitivity to detect
and image atomic 21 cm HI in individual galaxies at significant cosmological
distances, complementing ongoing ALMA imaging of redshifted high-J CO line
emission and far-infrared interstellar medium lines such as [CII] 157.7 um. At
frequencies below ~50 GHz, observations of redshifted emission from low-J
transitions of CO, HCN, HCO+, HNC, H2O and CS provide insight into the
kinematics and mass budget of the cold, dense star-forming gas in galaxies. In
advance of ALMA band 1 deployment (35 to 52 GHz), the most sensitive facility
for high-redshift studies of molecular gas operating below 50~GHz is the Karl
G. Jansky Very Large Array (VLA). Here, we present an overview of the role that
the SKA could play in molecular emission line studies during SKA1 and SKA2,
with an emphasis on studies of the dense gas tracers directly probing regions
of active star-formation.
