Autonomic dysfunction is common in Guillain-Barre syndrome (GBS). Here we report a case, which initially presented with an autonomic dysfunction causing fluctuation in blood pressure, confusion and a generalised tonic clonic seizure. MRI brain showed high T2 signal changes in posterior circulation consistent with a diagnosis of posterior reversible encephalopathy (PRES), which was treated with IV labatolol with good recovery. A week after this initial presentation patient developed acute flaccid limb weakness and respiratory muscle weakness requiring ventilatory support. Nerve conduction study performed showed prolonged distal latency and F wave latency consistent with acute GBS. Patient was treated with a course of IVIg for 5 days. This is the third case of PRES as the initial manifestation of GBS in adults. All three cases presented in the similar fashion raises the argument that these are not simply coincident but there must be a cause effect relationship between these two disorders. From practical point of view this case highlights two facts: (1) dysautonomia associated with GBS may precede motor weakness (2) PRES in absence of any other aetiological factor should prompt the search for underlying GBS.