It is hypothesized that with a constant percentage of reinforcement, resistance to extinction (RE) would be a function of the second-order uncertainty (H2), an informational measure, associated with the reinforcement sequence given. In Experiment I, 4 groups of rats received differential sequences of 50% reinforcement varying in H2 value. In Experiment II, 3 groups received reinforcement sequences of different H2 values, with the number of different N-lengths varied in the opposite direction. The RE was shown to be an increasing function of H2, supporting the proposed hypothesis relative to those by Capaldi et al.