Seizure activity is a known complication associated with multiple sclerosis; however, it may also result from side effects of the treatments for the disease. A 21-year-old man with Tourette's syndrome, pedophilia, Asperger's syndrome, and multiple sclerosis experienced seizures after receiving therapy with interferon beta-1a. Adjustments in his drug regimen led to the discovery of pseudoparkinsonism and other extrapyramidal symptoms. This case report illustrates how pharmacodynamic properties of drugs can complicate the treatment of neurologic disorders. Clinicians must be aware of the delicate balance between the signs and symptoms of disease states and the effects of drugs.