Forty-five patients with Williams syndrome (WS) were evaluated for oral abnormalities. The mean age of the patients was 9.25 years, the median age was 6.7 years, and the majority (62.2%) were male. Hypodontia was present in 11.1% of the patients. Abnormal tooth morphology was noted in 12.5% of the primary dentitions and 40.7% of the permanent dentitions. With the exception of the primary mandibular central incisors of males, all mesiodistal incisor crown dimensions were statistically significantly smaller when compared with norms (P < 0.05). At least one hypoplastic enamel defect was present in 9.4% of patients with primary teeth and in 18.5% with permanent teeth. No patients exhibited generalized enamel hypoplasia. More than half of the patients (59.1%) were both caries and restoration free, while only 13.6% presented with clinically active caries. Tongue thrusting was present in 67.7% of the sample, while more than 50% of the patients present with excessive interdental spacing. Patients exhibited a higher than normal prevalence of Class II and III occlusions, open and deep bites and anterior crossbites. No single dental finding was pathognomonic of WS, however two constellations of findings, each occurring in approximately one-third of the sample, were observed: 1) microdontia, anterior crossbite, tongue thrusting, and excessive interdental spacing, and 2) microdontia, deep or open bite, and excessive interdental spacing.