Electrophoretic studies of protein extracts from carrot calluses suspension-cultured on the media containing kinetin, BA, IAA, NAA or GA₃ at the levels of 10^(-6), 10^(-5), 10^(-4)M, respectively, were performed to identify polypeptides and proteins regulated by auxin, cytokinin or GA. Fifteen bands of polypeptide(s) were observed in the callus cultured in the control medium devoid of growth regulators, and their molecular weights were 18.₄, 20.₂, 20._0, 34._9, 35._7 37.₄ 40.₃, 44.₁, 44.₄, 44.₄, 49.₃, 55._0, 56._6, 58.₁, and 59._9 KD, respectively. The synthesis of polypeptide appeared to be promoted in two bands by kinetin, in six bands by BA, in one band by IAA, in two bands by NAA, and in four bands by GA₃, while inhibited in five bands by kinetin, in three bands by BA, in four bands by IAA, in three bands by NAA and in three bands by GA₃. The polypeptides of 40.₃ KD and 42.₂ KD seemed to be regulated by cytokinins, and those of 44.₁, KD, 37.₄ KD, and 56._6 KD by auxins. The proteins of three bands with relative mobilities of 0.56, 0.84, and 0.92, respectively, increased in the calluses cultured on the media containing kinetin, IAA, GA₃, NAA or BA, compared to the control, but it was difficult to identify the proteins specific for each growth regulator.