Piriformis syndrome remains a controversial diagnosis, despite its having first been described over 60 years ago. The controversy stems from several factors: variable and sometimes unclear cause, similarity to other more easily recognizable causes of sciatica, lack of consistent objective diagnostic findings, and relative rarity. Nevertheless, it is reasonable to infer that sciatic pain may be caused by compression anywhere along its length, from the spinal root level to the popliteal fossa, as is peripheral nerve entrapment elsewhere in the body. Pathologic changes at the greater sciatic notch may well be the source of sciatic pain and should be considered by the clinician. The diagnosis of piriformis syndrome remains one of exclusion, however, and in patients who present with sciatica, more common causes such as lumbar disease should be investigated and ruled out first. After excluding the most common causes of sciatica, physicians can use the criteria described here to investigate the possibility of piriformis syndrome. If properly diagnosed, it can often be treated effectively with either surgical or nonsurgical means.