The MS thesis option is available to highly qualified students but requires the student to find an adviser willing to supervise their research. In practice, availability of advisers is extremely limited and this option is exercised rarely.
With the approval of a supervising professor, qualified students may be allowed to pursue a thesis option. Students pursuing the thesis option must satisfy all of the policies and course requirements for the master's degree and, in addition, must enroll in a minimum of two semesters of CSCI 594a, CSCI 594b, CSCI 594z for a maximum of 4 units. Total units required for the degree with thesis is 32. The thesis must comply with all requirements set by the Graduate School. Students interested in a thesis while enrolled in a CS specialization should consult with their department adviser. Total units required for the M.S. in Computer Science general degree with thesis is 32. For specialized degree programs, the total unit requirement is 36. The thesis must comply with all requirements set by the Graduate School (http://www.usc.edu/schools/GraduateSchool/).
If you are in a CS specialization, please check with your advisor to determine if a thesis can be added to your program of study.