In this paper the general theory of multiway multiblock component and covar
iates regression models is explained. Unlike in existing methods such as mu
ltiblock PLS and multiblock PCA, in the new proposed method a different num
ber of components can be selected for each block. Furthermore, the method c
an be generalized to incorporate multiway blocks to which any multiway mode
l can be applied. The method is a direct extension of principal covariates
regression and therefore works in a simultaneous fashion in which a clearly
defined objective criterion is minimized. It can be tuned to fulfil the re
quirements of the user. Algorithms to calculate the components will be pres
ented. The method will be illustrated with two three-block examples and com
pared to existing approaches. The first example is with two-way data and th
e second example is with a three-way array. It will be shown that predictio
ns are as good as with the existing methods, but because for most blocks fe
wer components are required, diagnostic properties of the method are improv
ed. Copyright (C) 2000 John Wiley & Sons, Ltd.