There is a well established socioeconomic gradient in educational attainment, despite much effort in recent decades to address this inequality. This study evaluates a university access program that provides financial, academic and social support to low socioeconomic status (SES) students using a natural experiment which exploits the time variation in the expansion of the program across schools. The program has parallels with US affirmative actions programs, although preferential treatment is based on SES rather than ethnicity. Evaluating the effectiveness of programs targeting disadvantaged students in Ireland is particularly salient given the high rate of return to education and the lack of intergenerational mobility in educational attainment. Overall, we identify positive treatment effects on first year exam performance, progression to second year and final year graduation rates, with the impact often stronger for higher ability students. We find similar patterns of results for students that entered through the regular system and the 'affirmative action' group i.e. the students that entered with lower high school grades. The program affects the performance of both male and female students, albeit in different ways. This study suggests that access programs can be an effective means of improving academic outcomes for socioeconomically disadvantaged students. JEL Classifications: I21 There is a pronounced socioeconomic gradient in educational attainment, particularly at university level (see Digest of Education Statistics, 2007 for USA; Eurostudent, 2005 for Europe). Poor attainment by low socioeconomic status (SES) groups limits inter-generational mobility and reinforces socioeconomic inequalities. As there are many possible causes for such inequalities, including institutional barriers, low quality schooling, credit constraints or lack of parental investment, policies designed to address them vary considerably in their emphasis. Recent work has suggested the relative unimportance of credit constraints for university education in the US and the UK (Carneiro and Heckman, 2003; Dearden, McGranahan, and Sianesi, 2004) and emphasized the higher returns to early intervention in improving educational outcomes (Cunha and Heckman, 2007; Heckman, Moon, Pinto, Savelyev, and Yavitz, 2009b). Nonetheless, the most prevalent educational policy in most countries is targeted intervention programs by universities and colleges to boost enrolment and retention by disadvantaged social groups. While access programs are becoming increasingly diverse in their approach to tackling the barriers to progression and promoting success at university, the majority of programs focus exclusively on providing financial supports to students. Thus much of the literature, as demonstrated in a review by Deming and Dynarski (2009), concentrates on the effectiveness of financial aid programs such as the Pell Grant and the HOPE scholarships. There are also some programs that couple financial aid with other forms of outreach initiatives such as academic...