Williams syndrome (WS) is a well-known genetic disorder with a variable phenotype. In many cases, physical manifestations are subtle and may not be apparent at an early age, making diagnosis difficult in infants and young children who lack classic manifestations such as supravalvular aortic stenosis and hypercalcemia. Clinical suspicion is essential because the diagnostic genetic finding is not detectable on routine chromosomal analysis. Furthermore, early diagnosis allows for earlier detection and treatment of developmental, behavioral, and medical problems. In an effort to understand how and why individuals with WS are diagnosed, we conducted a survey-based study of parents of WS children. Packets containing a cover letter, consent form, parental survey and preaddressed stamped envelope were distributed to parents of children with WS. The survey included questions concerning initial diagnosis, WS findings present, medical specialists involved, and tests performed. Forty-six completed surveys were returned for analysis. The mean age at diagnosis was 3.66 years (SD 4.13). The mean age at which there were initial concerns was 0.98 year (SD 1.24) resulting in a mean delay in diagnosis of 2.77 years (SD 4.10). In addition, the involvement of a geneticists correlated with earlier diagnosis (2.26 years vs. 5.09 years without geneticist involvement, p = 0.03) and fewer tests ordered (5.2 vs. 8.2 in the nongeneticist group, p=0.0006). We observed a significant delay in the diagnosis of WS. Of note, the involvement of a geneticist was associated with earlier diagnosis and reduced number of tests.