A reasonably large number (39) of Mark-IA driver fuel cladding failures have been obtained from run-to-failure experiments in the Experimental Breeder Reactor II over the past few years. These experiments were designed to yield failure information for various design variables and to qualify the fuel element design to a burnup limit such that the risk of an end-of-design-life failure was exceedingly small for normal operating conditions. None of the design variables or operating conditions tested had a significant effect on the failure statistics. The failure mode fit the Weibull statistical failure model and is characterized by a burnup threshold of 3.0 at.% maximum burnup (BUmax), which must be surpassed prior to failure. The cumulative failure probability [F(BUmax)] for peak linear pin powers between 6.4 and 8.0 kW/ft and maximum cladding temperatures from 890 to 1050°F can be expressed as Once 3.0 at.% BUmax is achieved, it was also found experimentally that the failure rate could be decreased over a small burnup interval by lowering the power ratings. The Type 304L stainless-steel cladding in-reactor fracture mode for the Mark-IA driver fuel elements is characterized by inter granular crack propagation that originates at the outside surface of the cladding. This mode of failure appears to be assisted by stress corrosion and potentially deleterious grain boundary precipitation. Although the fracture mode is brittle in nature, uniform mechanical hoop strains >1% are achieved prior to failure.