In Chapingo, Mex. (Ll) and Cuapiaxtla, Tlax. (L2) in México, secondary growth in amaranth was evaluated in relation to the amount of rain during the reproductive growth period (GRP). 10 types of amaranth were evaluated in three sowing dates in L1 and 2 sowing dais in L2 in 1994. In general for all types of amaranth, when the rain was 289.7 mm during GRP, 82.8% of plants showed secondary growth; with rain of 225.2 mm during GRP, 74.2% of plants presented secondary growth; meanwhile with 162.1 mm of rain during GRP, secondary growth affected only 4.2% of plants. Finally, in L2 the rain in GRP was 118.2 mm without the presence of secondary growth.