The purpose of this study was to analyze the commercial paste opaque products currently available in domestic of foreign as well as domestic, such as Duceram Plus(DU; Ducera Dental GmbH, Germany), VMK 95(VM; Vita Co., Germany), Noritake EX-3(EX; Noritake Co., Japan) and Ceramax(CE; Alphadent Co., Korea). They were characterized in thermal expansion coefficient, particle size distribution, viscosity and solvent using thermomechanical analyzer, particle size analyzer, rheometer and infrared spectrophotometer. Experimental results are as follows; Firstly, thermal expansion coefficients were determined $13.9{ imes}10-6/^{circ}C$ for DU, $14.3{ imes}10-6/^{circ}C$ for VM, $13.3{ imes}10-6/^{circ}C$ for EX, and $14.0{ imes}10-6/^{circ}C$ for CE. Secondly, percent of partice size below $1{mu}m$ were 12% for DU, VM and CE, and 13% for EX, percent between $1{mu}m$ and $5{mu}m$ were 42% for DU, 42% for VM, 38% for EX, and 61 % for CE, percent between $5{mu}m$ and $10{mu}m$ were 21 % for DU, 24% for VM, 20% for EX, and 18% for CE, and over $10{mu}m$ were 25% for DU, 22% for VM, 29% for EX, 9% for CE. Thirdly, the basic composition of the solvent in all of the commercial paste opaques were determined as ethylene glycol from FT-IR investigation. Lastly, measured viscosities were 1798 cp for DU, 536 cp for VM, 1110 cp for EX, and 721 cp for CE.