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We propose a new method to improve the image quality and the encoding time of tree-structured vector quantization (TSVQ). We call this new method the closest-coupled tree-structured vector quantization (CCTSVQ). In this method, we use the closest-neighboring pointers to enlarge the search range of each search path and guide all search paths into more appropriate codewords. CCTSVQ therefore improves the image quality of TSVQ. This fact is shown in our experimental results. Furthermore, in these experimental results, we see that the encoding time of CCTSVQ is always faster than that of TSVQ, based on the same image quality.© 1997 Society of Photo-Optical Instrumentation Engineers.