Summary form only given. A technique is proposed for constructing multidimensional trellis codes that provides an alternative to Ungerboeck's method of 'set partitioning. ' The new codes use a signal constellation consisting of points from an n-dimensional lattice LAMBDA , with an equal number of points from each coset of a sublattice LAMBDA prime . One part of the input stream drives a generalized convolutional code whose outputs are cosets of LAMBDA prime , while the other part selects points from these cosets. This technique allows the path multiplicity to be calculated easily. It is also possible to describe methods of differential encoding very simply.