Recently, transradial angiography and intervention have been performed with high success rates and low rates of vascular complications. The incidence of compartment syndrome after the transradial approach seems to be very low. However, bleeding in the arm can occur and may lead to the devastating complication of compartment syndrome of the forearm, which if not treated early, can evolve into a disability of the arm. In fact, most cases of such complications are caused by guidewire- or catheter-induced damage to small arterial branches that are considerably proximal to the puncture site. However, we encountered a case of compartment syndrome that was not caused by bleeding or hematoma formation and required urgent fasciotomy for its treatment. The forearm wounds were left open to allow the edema to resolve and closed after 1 week. The patient recovered and was discharged, with full movement of his forearm and hand. We suspect that an arterial spasm induced by the radial sheath or catheter resulted in ischemia of the forearm muscles. To our knowledge, this is the first reported case in which acute compartment syndrome of the forearm occurred after transradial intervention and was not due to bleeding or hematoma formation. © 2009 Wiley-Liss, Inc.