Computer Science 50: “Introduction to Computer Science I” attracts 722 students to Sanders Theater. But although it is among the largest courses at Harvard, its online equivalent, Computer Science 50x, has drawn more than 100 times that number of students.

CS50x is one of two free courses offered by Harvard through edX, a joint nonprofit virtual learning initiative created last spring by Harvard and MIT.

The two courses offered by Harvard, which went live on Monday, are among the seven available from Harvard, MIT, and the University of California, Berkely in edX’s inaugural semester. Aside from CS50x, Harvard is offering Public Health 207x: “Health in Numbers: Quantitative Methods in Clinical & Public Health Research.”

E. Francis Cook, one of the professors leading Public Health 207x, described the number of enrollees—which has topped 30,000 so far—as “astounding.”

“This is the biggest course in public health ever offered in the world,” he said.

EdX President Anant Agarwal, an MIT professor, said that number is likely to grow even more, as students often register for online classes once the course materials have already been made available. Assignments in CS50x are due at the end of the course, allowing students to join as late as April, the same month that the course finishes.

The number of students who successfully complete the course could also be far lower than the number of students who enroll. Data from other online courses suggest that only 10 to 15 percent of enrollees complete the full requirements, according to Agarwal.

Harvard and MIT announced the creation of edX in May, hailing it as a groundbreaking endeavor to bring free academic courses to the masses. Each university invested $30 million in the project and invited other institutions to utilize the platform. University of California, Berkeley joined edX in late July, and the addition of the University of Texas was announced Monday.

MIT offered its own version of the edX platform prior to the creation of the joint venture. Approximately 160,000 students enrolled in its initial online course “Circuits & Electronics” this past spring.

Agarwal said that he anticipates that edX will unveil more than a dozen new offerings for the spring term in the next two weeks.

In anticipation of the first day of Harvard classes, Agarwal said he had his fingers crossed.

“We’re all in unchartered territory,” he said. “EdX team members, Berkeley, Harvard, and MIT faculty and students—everybody is working nights and weekends to get everything to work.”

—Staff writer Hana N. Rouse can be reached at hrouse@college.harvard.edu.

—Staff writer Justin C. Worland can be reached at jworland@college.harvard.edu.