The use of experimental animals, mostly rodents, in biomedical research and especially in oncology and immunology should be acknowledged with respect, recognizing the contribution of animal experimentation in the fascinating scientific progress in these disciplines of research. It is an obligation of the investigator to justify the scientific and ethical aspects of each study requiring the use of animals. The international guiding principles for using animals in biomedical research are well defined and have been distributed worldwide by the International Council for Laboratory Animal Science （ICLAS） since 1956, when this Organization was founded. In Poland the ICLAS philosophy and principles are highly respected and were implemented firstly by the members of the Commission on Biology of Experimental Animals appointed in 1962 by the Department of Medical Science of the Polish Academy of Science in Warsaw. Animal Protection Acts, first proclaimed in 1928 were gradually modified and improved. Actual legislation （enacted in 1997, 2003 and 2005） is consistent with EU Directives （86/609/EEC） and follows the internationally recommended principles that include ICLAS guidelines concerning animal welfare and care condition in biomedical research. The problem of ＂alternative methods＂ is briefly discussed.