Taking prescribed medications as intended, or ""adherence"" is an important strategy for the management of chronic diseases. Half of the individuals with a chronic disease have poor medication adherence, and research has shown that people with poor medication adherence often have more health problems, higher hospitalization rates and a higher risk of death. Not surprisingly, medication non-adherence is extremely expensive, and is estimated to cost the Canadian health care system $8 – 10 billion every year. With an estimated 75,000 Canadians affected, and three new people being diagnosed every day, Canada has one of the highest rates of MS in the world. Multiple sclerosis (MS) is a chronic disease of the brain and spinal cord, leading to disability, severe fatigue and coordination problems. Although there is no known cure, immunomodulatory drugs (IMDs), are now commonly prescribed for MS and can lead to a substantial improvement in the health of people with MS. The benefits of IMD therapy might not be realized in people who have poor adherence; currently very little information is known about adherence to these medications. Dr. Charity Evans is working to determine how many individuals with MS have good adherence to these medications, and if people with poor adherence have higher rates of hospitalizations or worsening of the disease. She will also work to identify any time periods during therapy when an individual is more likely to be non-adherent to their IMD. Dr. Evans will be using administrative health data from three provinces (British Columbia, Saskatchewan and Manitoba), and will be studying those individuals with MS who have received an IMD between 1995 and 2008. The results of this research study will be important to determine the impact that non-adherence may have on patient health outcomes in MS, and will also help identify factors to optimize adherence to MS therapies. These methods will also be applicable to the study of adherence in other chronic diseases requiring similar drug therapies.