This study aims to analyze the export competitiveness of the Thai garment industry inthe Japanese market during 1999-2005. In the first part, the analysis, using the ConstantMarket Share Model (CMS) of key factors for export competitiveness, shows that from100 garment products exported to the Japanese market, the major items which areusually made of synthetic fiber have been decreasing in export volumes, while theothers generally made of cotton, have been increasing in export volumes. The resultsalso show that volumes of exported garments have been depending on the World Tradeeffect, Commodity-composition effect and Competitiveness effect. In the second part,using the concept of National Competition Advantage, the competitiveness of garmentexporting businesses are classified into 3 groups: Excellent, Good and Fair. Thisclassification is based on the size of the business, design and quality of products, priceand market share, and efficiency of the firm's management and control.