The jaw musculature of notothenioid fishes is described and compared based on a total of 38 species referred to eight families of the suborder Notothenioidei. In the Notothenioidei, the adductor mandibulae, the largest and most conspicuous of the cranial muscles, is generally composed of sections A1, A2, A3 and Aw, as in the generalized percoids. The morphology of the adductor mandibulae is similar in most notothenioid families except the Nototheniidae and Bathydraconidae. Notothenia, Paranotohenia and Dissostichus are clearly distinguished from the other nototheniid genera in having A3. Gymnodraco or the Bathydraconidae has a fused A1-A2 complex and the anterior element is segmented by a tendinous intersection from the A1-A2 complex. These features are unique to Gymnodraco and not seen in other bathydraconids. The Harpagiferidae and Artedidraconidae share the same apomorphy, the presence of A1beta with the Nototheniidae and have no synapomorphies with the Bathydraconidae and Channichthyidae. The character distribution, however, shows some inconsistencies with the previous classifications. Based oil the limited evidence obtained ill this Study, the Notothenioidei can be divided into six groups and it seems reasonable to Suggest a review of the Current classification of the Nototheniidae.