-This paper is concerned with interframe coding of mono- chrome pictures using 3-dimensional transforms. First, an algorithm which enables the vector processing of 3-dimensional arrays is derived. Next, this algorithm is used in an interframe transform coding experi- ment. Picture data (6 bits/pel) is processed in (4 X 4 X 4) blocks using the Walsh-Hadamard transform (WHT), and the discrete cosine trans- (DCT). The corresponding reconstructed pictures (1 bit/pel) are included.