The intramuscular pressure at rest and during load in 25 symptomatic trapezius muscles was found to be higher than in 32 asymptomatic muscles. Operative findings in 4 patients revealed dense fibrosis around the muscle, including the accessory nerve, which might explain the increased intramuscular pressure. Fibrotic tissue release resulted in the relief of symptoms and normalized pressure both at rest and during load. We believe trapezius fibrosis may be a new entity to include in the neck-shoulder syndrome.