This document provides an introduction, conceptual framework, and curriculum guide for Mathematics I as part of the 2010 Secondary Education Curriculum in the Philippines. It was created by the Department of Education's Bureau of Secondary Education and Curriculum Development Division. The guide outlines the curriculum design process, which follows the Understanding by Design model. It also describes the results of refining the curriculum through pilot testing and stakeholder consultations to improve its relevance, rigor, and ability to promote student mastery.