The maxillary sinus communicates with the middle meatus of the nasal cavity through a narrow ostium. In this report, I survey the variations in the maxillary sinus anatomy of extant and fossil anthropoids, which has been investigated with computed tomography. A sinus that pneumatizes the entire maxilla is shared by all extant hominoids. In contrast, extant cercopithecoids lack this sinus, with the exception of Macaca, which has a small sinus. Cercopithecoids have a maxillary body filled with cancellous bone, except Papio and Theroputhecus, who lack this cancellous region. Extant platyrrhines have varied forms of the maxillary sinus: a sinus that pneumatizes the entire maxilla occurs in the atelids, Cebus, and Callicebus; a sinus that pneumatizes the medial part of the maxilla occurs in the callitrichines and Aotus; a sinus and expanded inferior meatus that pneumatizes the entire maxilla occurs in Pithecia; and the sinus is absent in Saimiri, Cacajao, and Chiropotes. The sinus was lost independently in the Saimiri and Cacajao-Chiropotes clades, and in a common ancestor of the cercopithecoids. It is argued that a sinus that pneumatizes the entire maxilla is the primitive feature in the anthropoids. This hypothesis is supported by studies of fossil anthropoids. Such studies that are presented in this paper are expected to stimulate future studies of the variations in sinus anatomy in prosimians and other mammals. Such information will potentially facilitate further phylogenetic analyses of unclassified fossil anthropoids