Wood as a natural material needs to be protected against biological and abiotic factors. Suitable combination for its protection seems to be a structural and chemical wood protection. In the past there were used various natural preservative coatings such as linseed or terebinthine oil, beeswax, lime, sea salt, beef cattle´s blood and others. These historical coatings were used to protect ceilings, carpentries and various furniture. In this Thesis we deal with historical oxen´s blood coating. We supposed its existence in two national cultural monuments – in Thurza' s House in Banská Bystrica and in Ľupča Castle in Slovenská Ľupča. Within the research, we took samples and prepared microscopic analysis to determine the wood species, health diagnostic of selected wooden elements and verifying of historical protective coatings. Various detectors of scanning electron microscope (SE, BSE, EDS) were used for microscopic analysis and evidence of oxen´s blood. Protective natural coatings can be used today as an environmentally friendly solution as well as an effective method against ligniperdous factors. The results from microscopic analyzes can help to preserve these objects for future generations.