Background. Metallic stent implantation is associated with an increased risk of adverse events, such as prolonged endothelial dysfunction, constant traumatisation of the vessel wall, chronic local inflammation and thrombosis. Thus, the development and manufacturing of bioresorbable stents, which maintain the required support during the vessel healing period and completely dissolve without any side effects, is highly relevant. At present, magnesium alloys are regarded the most applicable for this purpose due to their low corrosion resistance and high biocompatibility. Aim. To assess the cytotoxicity of different magnesium alloys in vitro. Methods. Using strain tempering, seven samples with different yield stress levels were produced: sample 1, MgZnZr (ZK60) 310 MPa; sample 2, MgZnCa (ZX10) 60 MPa; sample 3, MgZnCa (ZX40) 130 MPa; sample 4, MgYZn (WZ31) 300 MPa; sample 5, MgYZn (WZ31) 275 MPa; sample 6, MgYZn (WZ20) 340 MPa and sample 7, MgZnZr (ZK60) 180 MPa. The samples were incubated in a culture medium to obtain the extract, which was further tested on immortalised human fibroblasts. The cytotoxicity of the obtained extract was assessed using 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, optical microscopy and pH test. Results. In MTT assay, sample 7 was significantly cytotoxic (mean cell survival: 48% [2% ± 1%]), whereas sample 5 was slightly cytotoxic (mean cell survival: 81% [4% ± 14%]). In optical microscopy, the same samples showed the lowest cell density. In flow cytometry, the number of necrotic cells significantly increased in sample 7 (8.25%) and only slightly increased in samples 1 and 5 (3.449% and 3.626%, respectively). Furthermore, samples 5 and 7 showed the highest medium pH. Conclusion. The composition and strain tempering method magnesium alloys are directly correlated with the degree of cell necrosis, change in morphology and medium pH in vitro.