Pain patterns of the myofascial trigger points (TrP) for most muscles of the forearm have been documented. However, there are no published reports on the referred pain patterns for the pronator quadratus (PQ) muscle. The purpose of this study was to determine the referred pain pattern of the TrP in the PQ. Thirty-five arms of 35 healthy adult volunteers with no history of neck pain, arm pain or paresthesia were studied. Following skin sterilization, a Teflon-coated syringe needle was inserted into the PQ of the non-dominant forearm under electromyographic guidance, and 0.3mL of 6% hypertonic saline was injected. Subjects drew in their pain areas on a pain diagram, and this drawing was transferred into the Pain Chart System for analysis. Two main pain patterns were observed. The most common pattern involved pain spreading both distally and proximally from the injection site, along the medial aspect of the forearm (57%). In half of these cases, the pain area extended to the medial epicondyle proximally and the fifth digit distally. The second main pattern revealed pain spreading distally to the third and/or fourth finger (29%). The pain patterns originating from the PQ resemble the C8-T1 dermatomes, and ulnar and median nerve sensory distributions. Thus, myofascial pain of the PQ should be considered as a possible cause of pain in the medial forearm and hand, especially when no other neurological abnormalities are present.