A summary of known experimental results on in-reactor creep and irradiation growth is presented in terms of behavioural trends. The information is drawn primarily from observations in experimental and power reactors on various zirconium alloys and concentrates on new discoveries since the time of the last Conference on Fundamental Mechanisms of Radiation Induced Creep and Growth, Chalk River 1979. It covers the dependence of creep and growth on test conditions (neutron flux and fluence, temperature and stress) and material variables (composition, texture, cold-work, grain size and microstructure), together with irradiation-induced changes in density and microstructure. A brief account is given of the acceleration of growth in certain zirconium alloys at high fluences (growth breakaway) as well as evidence for breakaway creep. The role of internal stresses from thermo-mechanical treatments on irradiation growth behaviour is discussed. Reprinted from Journal of Nuclear Materials, Vol 159, Fidleris, V., “The Irradiation Creep and Growth Phenomena” pp. 22–42, 1988, with permission from Elsevier.