Modern medical technologies have developed many new devices that can be implanted into humans to repair, assist or take the place of diseased or defective bones, arteries and even organs. The materials, especially porous ones, used for these devices have evolved steadily over the past twenty years with TiNi-based alloys replacing stainless steels and titanium. The aim of the paper is to presents results for examination of porous TiNiMoCo-based alloy intended further to be used in clinical practice. Porous TiNi-based alloys showing shape memory effect were obtained by the methods of reaction and diffusion sintering with cobalt additives. From the results of the analysis of temperature dependences determined by the measurement of electrical resistivity and shape memory effect test, the effect of cobalt addition on the martensitic transformations in sintered body is described. The addition of cobalt during reaction and, especially, diffusion sintering, results in a decrease in the internal stresses in the TiNi phase. The addition of Co more than 1 at. % led to precipitation hardening of the alloy. Cobalt at concentrations studied in the work led to suppression of martensitic phase transformation.