This paper presents an intelligent CALI system called "Nihongo-CALI" (Japanese Computer Assisted Language Instruction), which employs natural language processing to provide immediate, grammatically sophisticated feedback to students in an interactive environment. Using this system, Nagata (1993) previously compared the effectiveness of the two different levels of computer feedback for teaching Japanese passive sentences: traditional feedback (which follows simple pattern-matching error analysis and indicates only missing/unexpected words in the learners' responses) and intelligent feedback (which utilizes a parsing technique to provide detailed grammatical explanations for the source of the learners' errors). The study found a statistically significant difference between traditional and intelligent feedback, favoring intelligent feedback. The present study compares the efficacy of intelligent CALI feedback with that of a more advanced, traditional CALI feedback (which also indicates the positions of missing particles in the learners' responses) for teaching basic sentence constructions in Japanese. The result indicates that the Intelligent CALI feedback is more effective than even the enhanced version of traditional CALI feedback, underscoring the importance of natural language processing technology in second language instruction.