Since starch can be split into maltose, the opinion has been widespread that starch is composed of chains of the maltose type1. Some authors, however, suggested a branched or netted structure2,3; comparative measurements of molecular weight and viscosity were definitely in favour of a branched structure. Haworth4, on the other hand, deduced from end-group assays that the molecular weight is low and therefore starch is composed of straight chains of not more than twenty to thirty glucose units. However, such a view could not be maintained. Some years ago it became quite evident5 that most starches are made up of two polysaccharides: one unbranched, for which we proposed the old name of ‘amylose’, and one branched, ‘amylopectin’.