The present invention relates to a novel truncated form of heptocyte growth factor (HGF) which specifically antagonizes the activity of HGF and to a novel truncated form of HGF that is a partial HGF agonist. In particular, the present invention relates to the purification, molecular cloning, recombinant expression of the truncated HGF variants and related pharmaceutical compositions. The present invention further relates to the utilization of the small HGF variants to either inhibit HGF mitogenesis or stimulate HGF mitogenesis in cells expressing the receptor for HGF.