Viscoplastic or yield stress materials are found in a lot of natural processes, and in a wide variety of industries such as food, cosmetic, farmaceutical and petroleum. In these industries, knowing the accurate rheological properties of a viscoplastic material and its behavior in different flows are fundamental for the success of many operations. Nevertheless, the rheometry of this kind of material still presents some challenges, such as yield stress measurements, apparent wall slip, thixotropy and the breakdown of structure on loading the material into the rheometer geometry used. In addition to that, until now some phenomena in different flows involving viscoplastic materials are not well understood, and therefore more investigation is required. This thesis deals with viscoplastic materials, their rheological properties measurements, and their behavior in different kinds of flow. Moreover, a detailed analysis of flows such as viscometric, expansions-contractions, the displacements in capillary tubes, and the displacements inside oil wells was performed.