Female pigs aged between one day (body weight 1.39 +/- 0.20 kg) and 1123 days (b.w. 233 +/- 32 kg) were allotted to 10 groups of various age and analyses of the concentration of DNA, RNA and protein in 9 different tissues were performed. The wet weight: DNA-, the protein: DNA- and the RNA: DNA-ratio were determined. With the exception of the liver the content in DNA, RNA and protein increased to the age of 1123 days. The highest fresh weight: DNA ratio of 2041 was reached on the 1123rd day in the M. longissimus; the smallest (111) existed at this time in the spleen. In the liver the highest content in fresh weight, in DNA and RNA was found on the 180th day. The smallest increases in the content of DNA and RNA in the mentioned period were in the brain, the highest in the spleen, the liver and the M. longissimus dorsi. The values can be used as a basis for studies on the influence of feeding and of diseases (infections) on growth.