This article presents findings from three opinion surveys conducted among representative samples of Mexico City residents: the first one immediately prior to the groundbreaking legalization of first-trimester abortion in April 2007, and one and two years after the reform. Bivariate and multivariate analyses were performed to assess changes in opinion concerning abortion and correlates of favorable opinion following reform. In 2009 a clear majority (74 percent) of respondents were in support of the Mexico City law allowing for elective first-trimester abortion, compared with 63 percent in 2008 and 38 percent in 2007. A significant increase in support for extending the law to the rest of Mexico was found: from 51 percent in 2007 to 70 percent in 2008 and 83 percent in 2009. In 2008 the significant independent correlates of support for the Mexico City law were education, infrequent religious service attendance, sex (being male), and political party affiliation; in 2009 they were education beyond high school, infrequent religious service attendance, and ever having been married.