The uptake of 1 μM14C-labelled arginine, glutamate, and alanine by cultured soybean (Glycine max L. cv. Mandarin) root cells was followed for periods up to 4 min at pH 5.5 in the presence of a 10 μM concentration of other amino compounds. From the degree of competition between 14C-labelled and unlabelled amino acids a number of uptake systems for basic, acidic, and neutral amino acids were identified, and a number of problems associated with amino acid transport in soybean cells were uncovered.