The glandular sensory organ found in representatives of all genera of Stilboncmatinae (Nematoda. Deslllodoridae) so far described was investigated by means of scanning and transmission electron microscopy. It is composed of onc type A and one type B glandular cell, onc l1lonocilialcd sensory cell, and a hollow seta. Whereas the Stilboncmatillae have eClosYI11biotic bacteria coating the cuticle, for an ollLgroup comparison three non-symbiotic species belonging to three genera from the closely related subfamilies Desmodorinae and Spiriniinae were chosen. In these three species the glandular sensory organ is composed of one type A glandular cell, one biciliated sensory cell, and a hollow seta. The consistent structure of a highly complex organ such as the glandular sensory organ with onc type B glandular cell and one monocilimed sensory cell suggests thut the Stilbonematinae are monophyletic in spite of their otherwise diverse morphology.