Two patients with ventriculoperitoneal shunts presented with symptoms of raised intracranial pressure indicative of possible shunt malfunction. During investigation, to eliminate this possibility, cerebral spinal fluid infusion studies were performed, which indicated proximal occlusion of the shunts in both cases. Retrograde flush of the ventricular catheter was performed during temporary compression of the siphon-control device, a manoeuvre which blocks distal flow. After the use of this technique, both patients' symptoms improved and they have remained symptom-free for over 2 years. This case report validates the role that infusion studies can play in clearing a blocked ventricular catheter shunt.