Magnetic resonance imaging (MRI) is a new and very powerful method for the diagnostics and monitoring of osteoarthritis. Its advantage is that all articular tissues can be visualized directly and are accessible for three-dimensional analysis. This article reviews qualitative, semiquantitative, and quantitative studies on articular cartilage with MRI. In particular we discuss pulse sequences and three-dimensional postprocessing methods for quantitative analysis of cartilage volume and thickness, along with their accuracy and precision in healthy volunteers and patients with osteoarthritis. it addition, we present approaches for quantitative analyses of structural/biochemical parameters and for the deformational behavior of cartilage in vivo.