Preliminary evaluation and screening of 62 introduced grain amaranth accessions was carried out at the Thailand Institute of Scientific and Technological Research (TISTR) Chan Thuk Research Station, 185 km NE of Bangkok. Twenty plants of each accession were planted monthly in single rows from April to August 1983. Plant responses were compared across morphological groups to facilitate general evaluation. When planting days were advanced, all morphological groups exhibited a similar response by initiating flowers earlier; total number of days to maturity was also reduced. In contrast, at later planting dates, maturity was delayed and plants were taller, perhaps as a result of the high rainfall normally found at that time of year. The grain amaranth was severely affected by insect pests. Without the use of insecticides, it was difficult to identify high‐yielding accessions. Accessions from all morphological groups exceptA. hypochondriacus, “Aztec” morphological group; andA. caudatus, “South American” morphological group, matured under the local conditions. However, the accessions ofA. cruentus, “Mexican” morphological group, were the most promising, as they exhibited growth characteristics suitable for commercial grain production. Profuse branching and a high degree of lodging were observed inA. cruentus, “African” morphological group;A. caudatus, “Edulis” morphological group;A. hypochondriacus, “Mercado” morphological group;A. hypochondriacus, “Nepal” morphological group; andA. hybridus, “Prima” morphological group. Flooding occurred in September 1983, which resulted in limited information for the last planting. Further studies are needed to determine suitable planting dates and optimum cultural practices, as well as any limiting factors that might emerge.