The relationship of leaf nitrate reductase (nr) and proteinase activities to the grain protein level and grain yield was investigated in four species of grain amaranth (Amaranthus hypochondriacus, A. caudatus, A. cruentus andA. edulis). A strikingly positive correlation between the leaf proteinase activity and the grain protein content was found.A. edulis with higher grain protein level possessed high leaf proteinase activity, whileA. hypochondriacus, with relatively lower grain protein content had lower leaf proteinase levels. Although there was no definite correlation between the leaf proteinase levels and the grain yield, the integrated leafnr activity was positively correlated with the grain yield. The total nitrogen content per plant seems to be dependent on the extent of root growth and the levels ofnr activity in leaves.