Abstract: A circuit for the fast calculation of the discrete cosine transform (X.sub.i), 0.ltoreq.i.ltoreq.N-1, in which N=2.sup.n and n is an integer of a signal defined by a sequence (x.sub.i), 0.ltoreq.i.ltoreq.N-1 includes a first adder stage receiving the sequence (x.sub.i), 0.ltoreq.i.ltoreq.N-1, and supplying two sequences (x.sub.i.sup.o) and y.sub.i.sup.i) and 0.ltoreq.i.ltoreq.(N/2)-1, a group of upper half-stages receiving the sequence of x.sup.o.sub.i) and supplying the sequence (X.sub.2q) of the even components of the cosine transform. That group constitutes a circuit for the fast calculation of the cosine transform for a group of (N/2) points and a group of lower half-stages receiving the sequence (y.sub.i) and supplying the sequence (X.sub.2q+1) of the odd components of the cosine transform.