The term 'vegetative state' is most appropriate for the state which develops when patients open their eyes after a comatose phase, without regaining consciousness. The definition and the diagnostic criteria from the Multi Society Task Force on Persistent Vegetative State are usable for the clinical practice in the Netherlands. The vegetative state must be differentiated from coma, locked-in syndrome and minimally conscious state. A systematic, multidisciplinary approach under the direction of a physician is key to diagnosing vegetative state. To this end, a clinical assessment is recommended with reassessment and verification of the diagnosis at appropriate moments. Careful observation remains the fundamental to the diagnosis.