The tooth-and-nail syndrome (Witkop's syndrome) is a rare autosomal dominant ectodermal dysplasia manifest by defects of the nail plates of the fingers and toes and hypodontia with normal hair and sweat gland function. We report a thirteen year-old girl who presented with marked longitudinal ridging of the nail plates of all ten fingers. The toenails were mildly ridged with koilonychia. Her mother's fingers were similarly affected to a lesser degree while her toenails appeared normal. Examination of the child's dentition revealed a hyperplastic frenulum and the absence of one of the usual four mandibular incisors. History provided by the mother described the maternal grandmother and maternal great aunt as having identical nail findings and the presence of only three lower incisors. Hair examination was normal in the mother and child, and no history or findings of sweat gland dysfunction was present. This report describes familial hypodontia, fingernail onychorrhexis, and toenail koilonychia consistent with Witkop's syndrome.