The constructive approach to mathematics has recently enjoyed a renaissance. This was caused largely by the appearance of Bishop's Foundations of Constructive Analysis, but also by the proliferation of powerful computers, which stimulated the development of constructive algebra for implementation purposes. In this book, the authors present the fundamental structures of modern algebra from a constructive point of view. Beginning with basic notions, the authors proceed to treat PID's, field theory (including Galois theory), factorisation of polynomials, noetherian rings, valuation theory, and Dedekind domains.