A cytologically distinct group of cells in the rostral mesencephalic reticular formation was strongly labelled by injections of anterograde tracer substances into the caudal paramedian pontine reticular formation (PPRF) of the monkey. The cell group lies ventral to nucleus of Darkschewitsch (nD), rostral to the interstitial nucleus of Cajal (iC) and the tractus retroflexus (TR). It receives inputs from areas which control eye movements, PPRF and the vestibular nuclei, and sends efferents to the oculomotor nucleus. Physiological, anatomical and clinical evidence support the conclusion that this cell group is involved in the generation of vertical eye movements. In an attempt to be anatomically specific the name rostral interstitial nucleus of the medial longitudinal fasciculus (rostral iMLF) has been used.