Oculomotor nerve paresis is a rare neurological manifestation in rheumatological disease. It is most commonly described in connection with systemic vascular disease such as polyarteritis nodosa, Wegener's granulomatosis and Behçet's disease but is rarely an isolated symptom. As in benign vascular and diabetic oculomotor paresis, the etiology of oculomotor paresis in rheumatic disease appears to be angiopathy and subsequent ischaemia in the nerve tissue. Two case histories are presented. Both of the patients had been recognized as having well-defined rheumatological complaints without previous neurological manifestations. Both developed partial isolated affection of the oculomotor nerve with paresis of the levator palphebrae muscle and ptosis. The condition was interpreted as mononeuritis of vascular origin and the patients were treated with methylprednisolone parenterally (1 g methylprednisolone per 250 ml isotonic sodium chloride per 24 hours for a total of three days). In the subsequent discussion, the neuroanatomical relationships of the oculomotor nuclear complex in the mesencephalon are described together with the fasciculi and the course of the peripheral nerve. On the basis of selected case histories, the possible anatomical localization of the lesion in oculomotor paresis of vascular origin is discussed.