This paper describes static tests of tubular specimens of medium steel under biaxial stresses and at room temperature. The purposes of the tests were: (1) to obtain an experimental check on the so-called “third rule of plastic flow;” (2) to study the absorption of energy as a function of the biaxial stress ratio; and (3) to determine the effect of the path of loading as symbolized by the strain path. Within the range of conditions investigated, the path of loading was found to be immaterial. A relation between strain energies absorbed under biaxial and uniaxial stress states up to a common maximum strain is tentatively formulated.