Now in its Fourth Edition, this book presents a systematic approach to solving dosage calculation problems using dimensional analysis. The book incorporates the simple to complex approach, focusing on understanding how to problem solve. Use of the "Unit Path" creates a picture in the reader's mind, simplifying the process and significantly reducing the chance of error. Other pedagogical features include numerous practice problems, examples of actual drug labels, and case studies. This edition's practice problems are organized into medical-surgical, pediatric, psychiatric-mental health, and maternal/neonatal/women's health. More pediatric case studies are included. This edition also includes a pre-test and two post-tests.