As part of MDRC's multisite Opening Doors demonstration, Chaffey College, a large community college in Southern California, ran two versions of a program that was designed to improve outcomes among students who are on probation. Both versions offered a "College Success" course, taught by a college counselor, which provided basic information on study skills and the requirements of college. The original program, called "Opening Doors," was a one-semester, voluntary program. The other version, called "Enhanced Opening Doors" in this report, was a two-semester program, in which students were told that they were required to take the College Success course. In 2005, students were randomly assigned either to a program group that was eligible for Opening Doors or to a control group that received standard college courses and services. In 2006, a second group of students was randomly assigned to estimate the impacts of Enhanced Opening Doors. This report describes the findings for both programs, which include the following: (1) Chaffey's original, voluntary Opening Doors program did not meaningfully affect students' academic outcomes; (2) In contrast, the Enhanced Opening Doors program, with its message of required participation, improved students' academic outcomes; and (3) Analyses suggest that the greater success of Enhanced Opening Doors might have been driven by the higher rate of participation in the College Success course. Following the study, Chaffey committed to institutionalizing a revised version of Enhanced Opening Doors to more fully implement and enforce the college's probation and dismissal policies, and built upon its experiences in the Opening Doors demonstration to develop a voluntary program, called "Smart Start," for new students who are at risk of experiencing difficulties. Appendices include: (1) Supplementary Tables for Chapter 2; (2) Survey Response Analysis; (3) Description of Scales Presented in Chapter 3; (4) Supplementary Tables for Chapter 4; (5) Description of Scales Presented in Chapter 4; (6) Supplementary Tables for Chapter 5; and (7) Supplementary Tables for Chapter 6. (Contains 46 tables, 8 figures, 5 boxes, and 4 footnotes.)[ Other sponsoring agencies include: The Kresge Foundation, Sandler Foundation, and The Starr Foundation.