OBJECTIVE: To develop a measure of treatment satisfaction that assesses attributes specific to injected medications for multiple sclerosis (MS). METHODS: Item development for the MS Treatment Satisfaction Questionnaire (MSTCQ) was initiated with review of MS websites, literature, adverse effects, as well as interviews and focus groups with MS patients. Pilot testing resulted in aggregation of items postulated to assess adverse effects, difficulty of use, inconvenience, and discomforts. The MSTCQ test instrument included nine items describing “Satisfaction with the Injection System” and 11 items describing “Side Effects.” The instrument was completed by 317 patients, ages 18-60 years, who had been using interferon-beta-1a subcutaneously for > six-months. RESULTS: The “Satisfaction with the Injection System” subscale fit a one-component solution with internal consistency coefficient with good cross-sectional reliability (a=0.70). A principal components analysis of the 11 items assessing “Side Effects” resulted in a three-component solution: flu-like side effects (a=0.82); injection-site reactions (a=0.68), and global items (a=0.75). Test-retest reliabilities at one-week (N=55) were Satisfaction r=0.68 (intraclass correlation coefficient); Side Effects: flu-like side effects, r=0.86; global evaluation of side effects, r=0.77; injection site side effects, r=0.73. Almost all correlations were statistically significant (p<0.001). Correlations with demographic variables showed significant associations with the MSTCQ total and subscale scores. Age, falling behind in work and home activities, and level of activity/independence exhibit the most consistent relationships to the various MSTCQ measures. CONCLUSIONS: The initial development and testing shows that the MSTCQ should provide insight into the concerns of MS patients about their use of injected medications. These data indicate that older respondents and respondents who are relatively more active and independent have a more favorable view of their MS treatment.