This chapter provides an overview of the rheological characterization of tomato-based products, the importance of which is related to processing design, quality control, and sensory acceptance. First, we present some general principles of rheology, covering the fundamental concepts and rheological classification of fluid foods. Then, we discuss steady-state shear, time-dependent, and viscoelastic properties. Each of these is discussed separately, focusing on tomato products and presenting the equations generally used to model rheological behaviour and their respective parameters. In addition, some factors that influence rheological characteristics are presented, including the composition and characteristics of the product and the processing conditions.