Nowadays, our understanding of the role of educational assessments has shifted from summative assessments to formative assessments. Technology has played an important role in this transition, and computer-based assessments have become popular these days. Echoing this global transition, China's Ministry of Education (CMOE) initiated a reform in the English curriculum at the college level, with calls for valid and reliable computer-based formative assessments to be implemented in college classrooms. Curriculum-based measurements (CBMs) have great potential as reliable and effective formative assessment tools in English-language learning. However, few studies address the application of CBMs to foreign language-learning contexts. Motivation affects the validity of an assessment, and gamification is a commonly-used approach to increase students' motivation in online learning and assessment environments. Although the literature indicates that gamification generally has a positive effect on students, some studies suggest specifically other results. Therefore, this study investigated the use of gamification in a computer-based CBM system. Avenue: PM, a gamified CBM English assessment system, was used in the current study. Avenue: PM has several game elements, including progressive levels, progress bars, points, goals, and animated animals. A version of Avenue: PM with no gamification was also designed for this study. Three hundred forty-two students recruited from a regional Chinese college participated in the study. All students were randomly assigned to the control group or the treatment group to use the system for at least 10 minutes for six weeks. The control group in this study used Avenue: PM without game elements (non-gamified system) and the treatment group used Avenue: PM with game elements (gamified system). Students' satisfaction with the system was also scored using a survey at the end of the study. The results indicate that the students using the gamified system spent more time and performed better on the assessments compared to the students using the non-gamified system. However, no difference in student satisfaction with the system was found. In summary, this research provides evidence of the positive effect of gamification on student participation and performance in the context of an online English assessment system. The study also provides some implications for the future design and development of gamification applications. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]