The discriminative assumption on buildup of proactive interference in short-term memory predicts that when intertrial similarity of items is high, the proactive interference is built up while interlist similarity of items is low, the proactive interference is not built up. To test the discriminative assumption in Japanese Kanji learning, intertrial similarity was changed by the acoustic, the radical (as one of the figurative properties), and the radical plus semantic properties in Kanji. For the acoustic and the radical plus semantic properties, the proactive interference was built up in the non-discriminative list with high intertrial similarity but not built in the discriminative list with low intertrial similarity, which supported the prediction. The prediction was not supported for the radical property. The findings were discussed with reference to the discriminative function of these properties as memory cues.