Application of the small-fibre excitant and inflammatory irritant mustard oil or the excitatory amino-acid receptor agonist glutamate to the rat temporomandibular joint (TMJ) region evokes similar changes in jaw-muscle activity, suggesting that peripheral application of glutamate may be nociceptive. Application of mustard oil to the TMJ region is also inflammatory, but, it is not clear if application of glutamate is equally inflammatory. In this study the extent of plasma-protein extravasation and oedema induced by mustard oil application to the TMJ region was compared with that induced by glutamate. Application of mustard oil resulted in plasma-protein extravasation into the TMJ tissues and oedema of the TMJ region. In contrast, glutamate did not cause plasma-protein extravasation or oedema.