Protein and energy value of 6 samples of "Spirulina" was studied on growing rats in 1972 and 1973. Sample RL 1(Spirulina platensis, originating from Tchad) was grown in artifical conditions in a laboratory. Others samples (Spirulina maxima) were grown in the solar evaporator near Mexico, washed and dried either on heated rollers (MR8, MR13) or by spraying (MA 7, MA10). Sample MA10 D corresponds to sample MA10, bleached by ethanol plus acetone (Baron, 1975). Each Spirulina sample was the only protein source of balanced, starch diets. The diets were supplemented in essential amino acids (E.A.A.) according to the requirements of growing rats (table 1). The ratios [(digestible nitrogen/metabolisable energy (EM] of the Spirulina diets were similar to that of the control diets containing herring meal. The diets were fed to groups of 15 to 17 growing rats. Energy and nitrogen balances were established by the comparative slaughter technique. Blood and muscle samples were taken at slaughter for the determination of free amino acids levels.