In some areas of the Regional Educational Laboratory (REL) Pacific Region, between one-fourth and a half of secondary school-age students are not enrolled in school. Not being enrolled in school or being chronically absent can have lasting effects on students' economic and social development. This REL Pacific report summarizes research on nonenrollment and chronic absenteeism from the United States and emergent nations that share characteristics with Pacific island nations. Four types of factors influence student nonenrollment and absenteeism: student-specific, family-specific, school-specific, and community-specific. Many of these potential factors are interconnected, and the effects of these factors may vary by region. Therefore, educators, policymakers, and family and community members in the Pacific Region may need to gather additional data in order to explore these factors in their own communities. Stakeholders can also use this review to begin to identify the root causes for why students are not in school in order to develop and implement targeted strategies to support student enrollment and attendance. The following are appended: (1) Calculating the net enrollment rate; (2) Net enrollment rates in Pacific island nations; and (3) Data collection and methodology.