Tardigrades belong to the most desiccation-tolerant animals on Earth, and are able to lose practically all water in their cells without dying. Recent investigations have also confirmed a seminal study from 1964 showing that tardigrades have an extraordinary tolerance also to ionizing radiation. The biochemical and physiological mechanisms behind these two tolerance phenomena, and the possible functional link between them, is currently not understood. However, the finding that desiccated and non-desiccated tardigrades show similar tolerances to ionizing radiation suggests that radiation tolerance in these animals is not a physical function of the dry state. Rather, both mechanisms preventing damage and mechanisms repairing damage to cell components are likely to be involved. The possible involvement of DNA repair mechanisms in tolerances of anhydrobiotic animals make them of special interest for understanding naturally evolved adaptations for coping with environmental agents inducing damage to DNA. I will summarize our current knowledge about radiation tolerance in tardigrades and other anhydrobiotic animals, discuss some of its implications for our understanding of desiccation tolerance, and also present some recent data on radiation tolerance in tardigrade embryos.