It has been proved that intramuscular fat (IMF) or marbling in beef improves palatability. Recently, consumers have considered not only the degree of marbling but also the size and distribution of marbling flecks for their health and appetizing looking of beef. Computer image analysis (CIA) systems have been developed to assess various characteristics of marbling particles (MPs) such as the number, size, and distribution (fineness or coarseness) objectively. Some CIA indexes about MPs indicating how MPs are distributed evenly had significant positive relationship with price which represents consumers’ interest. RNA-seq research about formation of fine MPs in the longissimus thoracis (LT) muscle tissue of cattle have not yet been tried in transcriptome level. This study was conducted to reveal the DEGs between groups which have high or low number of fine MPs in the Longissimus thoracis muscle of Korean beef cattle and to understand molecular events associated with marbling fineness. Overall design: mRNA profiles of each three LT samples from high and low number of fine MP groups were generated, and DEGs were anayzed.