The oral manifestations of glossitis, stomatitis and mucosal ulceration in vitamin B12 deficiency have long been recognised. These oral changes may occur in the absence of symptomatic anaemia or of macrocytosis. The aim of this paper is to describe a retrospective study of the wide range of oral signs and symptoms reported by 14 patients found to have a previously undiagnosed vitamin B12 deficiency. None of the patients described in this study had generalised symptoms sufficiently advanced to arouse suspicions of vitamin B12 deficiency. The essential criteria for the diagnosis of pernicious anaemia are also discussed.