Effects of repetitive listening to unknown speech (artificially prepared) on ear differences in emotional evaluation were examined with normal twenty-five university students. The subjects were given unknown speech in which white noise was played to one ear and artificially prepared unknown speech to the other ear nine times in total for two weeks, and were asked to evaluate both category of emotonal tone (positive or negative) and strength of emotionality. The results revealed following points; 1) Evaluation of emotional tone strength changed with repetitive listening. Especially, for negative tone speech, the strength of emotionality increased with repetitive listening in the left ear while no change was shown in the right ear. On the other hand, for positive tone speech, the strength of emotionality did not change with repetitive listening in both ears, 2) In some cases, evaluation of emotional tone category changed with repetitive listening. In these cases, there was a tendency that categorization into negative tone shifted to positive categorization in the left ear. These findings are discussed in relation to the differential hemisphere specialization for unknown speech emotionality evaluation.