Special Topic Issue: Cells Tissues Organs 2003, Vol. 174, No. 1-2 Temporomandibular (jaw) joint diseases and disorders are estimated to affect 10 million Americans every year with the majority of those seeking treatment being women in their childbearing years. Researchers generally agree that the most common temporomandibular diseases and disorders fall into three main categories: arthritis, internal derangement of the joint, and/or myofascial pain. This special issue of Cells Tissues Organs is a selection of papers presented at the second meeting of the Temporomandibular Joint Association held in May 2002. The meeting focused on the role that osteoarthritis and muscle mechanics play in temporomandibular joint diseases and disorders. Currently there are no established treatments for temporomandibular joint conditions, so that the therapies patients receive generally reflect the personal views and practices of the provider. These papers will serve as a reference for clinical and basic research in this field, as well as a stimulus for future investigations. Clinicians dealing with chronic musculoskeletal disorders such as arthritis will benefit by expanding their perspective to include new knowledge about their fields as well as about similar disorders of the head and neck. Basic and translational researchers in the same fields should read these papers because we hope that this will encourage them to evaluate both the unique and the generalized features of research related to temporomandibular disorders.