This booklet summarizes the mathematics chapter from "Handbook of Research on Improving Student Achievement", published by the Educational Research Service (ERS). The Handbook is based on the idea that, in order to succeed, efforts to improve instruction must focus on the existing knowledge base with respect to effective teaching and learning. The Handbook was specifically designed to help school administrators and teachers carry out their evolving instructional leadership roles by giving them a ready source of authoritative yet practitioner-based information about research on effective teaching and learning. The practices identified in this booklet reflect a mixture of emerging strategies and practices in long-term use. The research supporting each practice is briefly summarized, how this research might be applied in actual classroom practice is described, and the most important studies that support the practice are listed. A complete list of references is provided at the end of the booklet for readers who want to study and understand the practices more fully. The research findings presented in this booklet provide a starting point for developing comprehensive school plans to improve mathematics instruction. (Contains 98 references.) (ASK)