Boron is known to induce persistent liquid phase sintering when added to austenitic stainless steel powders. In the present investigation additions of boron to 316L stainless steel, and their influence on tensile and impact properties, were investigated. Boron induces two main microstructural modifications which strongly influence the mechanical behaviour of the material. One, it increases density, and two, it gives rise to the formation of grain boundary eutectic borides. Whereas an increase in density is positive, the influence of the borides is negative because they fracture during plastic straining, reducing both ductility and strength. The influence of density and borides on the plastic behaviour of the materials was then analysed in detail with reference to a simple damage model. It is further observed that with the addition of 0.2w/oB, density shows a noticeable increase and the negative effect of borides on the mechanical properties is reduced because of their lower amount and discontinuous morphology. This material may therefore be suitable for technological applications, because of its improved mechanical properties and because of the presence on the surface of the specimen of a homogeneous layer in which pores are practically absent; this promotes good corrosion resistance.