The Interactive Mathematics Program (IMP) is a growing collaboration of mathematicians, teacher-educators, and teachers who created a four-year program of problem-based mathematics to replace the traditional Algebra I-Geometry-Algebra II/Trigonometry-Precalculus sequence. The IMP curriculum integrates traditional material with additional topics, such as statistics, probability, curve fitting, and matrix algebra. IMP units are generally structured around a complex central problem. Although each unit has a specific mathematical focus, other topics are brought in as needed to solve the central problem, rather than narrowly restricting the mathematical content. Ideas that are developed in one unit are usually revisited and deepened in one or more later units. Supported during its development by the National Science Foundation, one link is to the publisher's website and another is to the project site.