Capsicum annuum seeds were pretreated with three concentrations of α-naphthaleneacetic acid (NAA). The fruits of the control and treated plants showed differences in the quantities of free amino acids during three developmental stages. From a relatively high amount of total free amino acids in the early phase of fruit development, there was lowering in the mid-phase and further lowering in the terminal phase. There were eight prominent ninhydrin-reacting spots which were identified as tryptophan, glycine, glutamic acid, valine-methionine, γ-aminobutyric acid, leucine(s), alanine, and aspartic acid and eleven trace spots attributable to tyrosine, serine, lysine, asparagine, cystine, thrconine histidine, phenylalanine, arginine, glutamine, and ornithine. Hormone treatment tended to decrease the total amino acids in the early- and mid-phases of fruit development compared with the control fruits. Aspartic acid was present in greater quantities in the treatments than in the controls. In the terminal phase, the treated fruit did not show any significant change in the total free amino acid contents. The significance of the NAA-included variation in free amino acids is discussed.