Spirulina is a cyanobacteria which is among the oldest forms of life on earth. For centuries it has been eaten by certain primitive populations from Africa and America and scientists have taken an interest in it for several decades because of its nutritional wealth and therapeutic significance. Rich in proteins, vitamins, trace elements and complex molecules, Spirulina helps to protect against certain nutritional deficiencies. Scientific research from many countries has given prominence to the part it plays in the prevention of cancer, cellular ageing, infectious diseases and reduced immune system, as well as playing an important part in the functioning of the medulla (stimulation of the erythropoiesis). Spirulina has not given away all its secrets yet and it is likely that further research will help to discover more therapeutic uses in the near future. © Springer 2005.