While a number of randomized double-blind controlled trials have demonstrated the value of zonisamide in the treatment of seizures, such studies lend limited insight into the efficacy and tolerance of zonisamide in real-world clinical practice. Furthermore, randomized trials tend to inquire about negative effects, such as adverse reactions, while positive effects such as improvement in mood, or sense of well-being are not similarly categorized. In addition, there is little information about experience with zonisamide specifically in adult patients with mental retardation (MR) / developmental disabilities (DD). Anecdotal experience suggests that zonisamide is exceptionally well-tolerated, and is associated with an improved general sense of well-being and quality of life in non-DD patients. In patients with MR/DD, observational studies that promote awareness of such distinguishing features and other aspects of efficacy are essential for guiding decision-making when prescribing antiepileptic drugs.