Polyurethanes are among the most widespread polymer technologies and account for about 5% of all plastics produced worldwide. This review covers the technology of polyurethane building block production and physical properties, the fundamental science underlying reactivity and polymer properties and industrial applications. Specifically covered are isocyanates, polyols, elastomers, foams, coatings, adhesives, thermoplastics, recycling, and health and environmental issues. Industrial size, participants, and trends are also reviewed.