This article focuses on mechanical behavior of materials under conditions of uniaxial tension and compression. The emphasis is on mechanical behavior during the engineering tension test, which is used to provide basic design information on the strength of materials and as an acceptance test for the specification of materials. The article presents mathematical expressions for a flow curve of many metals in the region of uniform plastic deformation. It explains that the rate at which strain is applied to the tension specimen has an important influence on the stress-strain curve. The point of necking at maximum load can be obtained from the true stress-true strain curve by finding the point on the curve having a subtangent of unity. The article concludes with an overview of the ductility measurements performed by notch tensile and compression tests.