Williams syndrome (WS) is a neurodevelopmental genetic disorder characterized in part by anxiety and behavioral difficulties. We examine the effectiveness and adverse effects of antidepressant, anxiolytic, and antipsychotic medications in individuals with WS. A total of 513 parents/caregivers completed a survey of psychotropic medication usage regarding their child or adult with WS. Twenty-four percent (24%) of the individuals had been prescribed an SSRI medication, while 12% had been prescribed another type of antidepressant or anxiolytic. Overall, 81% of respondents indicated that SSRI medications were either "Helpful" or "Somewhat Helpful", with paroxetine reported to be the least helpful. Sixty-four percent (64%) of survey participants reported that non-SSRI antidepressants and anxiolytics were either "Helpful" or "Somewhat Helpful" in treating symptoms of anxiety. Side effects for the antidepressants and anxiolytics were typically neurological in nature. Ten percent (10%) of the survey participants reported taking an antipsychotic medication, with risperidone and quetiapine described as more helpful than aripiprazole. Medication effectiveness may be related to the impact on serotonin levels. These findings call for further studies of medication usage in WS in order to improve their quality of life. (Contains 9 tables and 1 figure.)