To investigate iodine stress corrosion cracking on the behavior of Zircaloy tubing, a standard test procedure with internally pressurized creep specimens (I-SCC standard test) and a split-ring test (I-SCC laboratory test) were developed. The threshold value for brittle cracking in iodine is 10^-6 g iodine per square centimetre. The uniform elongation shows a clear minimum in its dependence on strain rate. Basal pole orientations in the range of ±50 to ±70 deg relative to the radial direction are the most I-SCC sensitive textures. The I-SCC process occurs in several stages; incubation, crack nucleation, and propagation. A thermodynamic evaluation indicates that I-SCC only occurs when zirconium iodides condense on the Zircaloy surface. Results show that comparisons of the I-SCC susceptibility of tubing manufactured in different manners should be made at the same point on the strain rate versus uniform elongation curves; for example, at the strain rate with the minimum of uniform elongation.