The elucidation of transmembrane spanning domain structure is still a challenging experimental problem in protein chemistry. Several important proteins belong to the membrane protein group from which we have chosen the ionotropic glutamate receptor activated by N-methyl-D-aspartate as the subject of our work. This heteromeric protein has a broad range of important physiological functions and seems to be involved in pathological entities. A better knowledge of its sequence and possible structure may help understand its different physiological roles and might be useful for the design of drugs to treat disorders in which it is involved. The present work predicts the sequence of the transmembrane spanning segments of the different receptor subunits using different available algorithms. It compares the predictions obtained with the few published experimentally determined segments, finding good agreement between them.