Interlanguage: 40 Years and Later, which was held from October 5 to 7, 2012 at the Cowin Center of Teachers College, Columbia University, was organized by the Roundtable in Second Language Studies to celebrate the 40th anniversary of the Interlanguage Hypothesis. Ten renowned researchers shared their thoughts on the hypothesis, explored the issues, and updated the ideas. They included Elaine Tarone, Terence Odlin, ZhaoHong Han, Silvina Montrul, Lourdes Ortega, Kathleen Boadovi-Harlig, Susan Gass, Charlene Polio, Bill VanPatten, and Diane Larsen-Freeman. Speakers had 60 minutes to give their talks, which were followed by 30- to 45-minute question-and-answer sessions. At the end, Larry Selinker, who coined the term interlanguage, gave the concluding speech.