The teaching of English as a second language (ESL) to adult learners in the 21st century focuses on a combination of oral and written skills geared toward success in a variety of settings, including the workplace and post-secondary institutions. The study was intended to determine if specific curricular components recommended for syllabus design, Knowles andragogical assumptions, and TESOL adult teaching standards were present in the curriculum designed for adult ESL learners. The study involved examining ESL curriculums of basic and business courses from public and private institutions in Puerto Rico using qualitative research methodology. The purpose of this study was to explore the presence of recommended curricular structures, andragogical principles, and International TESOL standards in curriculums used in the teaching of adult ESL learners. The curriculums were examined using three checklists: components of the curriculum, Knowles andragogical assumptions, and the adult TESOL Standards to determine if these were considered in the construction of the syllabi examined. The findings may expand knowledge related to the integration of andragogy and the standards of adult ESL, as well as research-based curricular structures, into post-secondary settings. The review results indicated that the curriculums of public and private institutions generally followed recommended ESL syllabi guidelines and the ESL adult standards. However, Knowles' principles were integrated in the business courses only. Syllabi revision and uniform integration of Knowles principles into curriculum design and the regular updating of the contents of the courses are two important recommendations. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]