The objectives of this dissertation include describing and analyzing the patterns of inequality in ALE participation at both the micro and macro levels. Special attention is paid to social origins of individual adults and their association with two groups of macro-level factors, social inequality (income, education, and skill inequality) and institutional settings (SEP, ALMPs, stratification, and TUD), across twelve selective OECD countries. In addition, this dissertation develops a deeper understanding of policy dimensions of inequality in ALE participation. A focus is placed on the historical development of ALE policies and the policy environment in Korea, Finland, and the U.S. that may serve as a component of the political, social and economic factors affecting ALE participation. To achieve these objectives, both quantitative (binary logistic regression and multilevel analysis) and qualitative methods (multiple case study) are employed. This investigation finds that the advantage of social origins in ALE participation is present across countries, to varying degrees. The advantage of social origins in NFALE and JRNFALE participation is associated with income and education inequality. It is associated with education inequality in FALE participation. For institutional settings, public spending on ALMPs and TUD are negatively associated with the advantage of social origins in NFALE and JRNFALE participation only. The multiple case study indicates that convergence in ALE policy and policy environment is identified in the three countries: predominance of market-driven ALE and job-related ALE, the decentralization of the ALE system, and decreasing public support. Lastly, an effort was made to relate the findings from the quantitative analyses to the analysis of the historical development of the ALE policy environment to provide reasonable background to explain inequality in ALE participation along with the three elements of neoliberal ideology, HRD-driven ALE policy, individual responsibility and the withdrawal of the State. In a market-driven policy environment where individual adults should take responsibility for their education and training with decreasing public support for education, adults with low social origins are less likely to participate in ALE. Ultimately, as ALE is a multi-dimensional issue concerning its roles and objectives, a comprehensive approach is required to address inequality in ALE participation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]