We present an efficient algorithm for the problem of online multiclass prediction with bandit feedback in the fully adversarial setting. We measure its regret with respect to the log-loss defined in [AR09], which is parameterized by a scalar . We prove that the regret of N EWTRON is when is a constant that does not vary with horizon T , and at most if is allowed to increase to infinity with T . For , the regret is bounded by , thus solving the open problem of [KSST08, AR09]. Our algorithm is based on a novel application of the online Newton method [HAK07]. We test our algorithm and show it to perform well in experiments, even when is a small constant.