The evaluation of hydrocephalic shunts is a common problem seen in emergency departments. The emergency medicine practitioner must be aware of the various types of apparatus, the functional considerations of the shunt, and the potential complications of obstruction. Shunt malfunction, either from obstruction or infection, can be life-threatening, and a reasonable approach for delineating the underlying problem and its severity is presented. Close involvement of the neurosurgeon is imperative because definitive care is almost always the purview of the consultant.