An image analysis technique was developed to determine the degree of marbling of cattle meat. This measure was determined in Longissimus dorsi muscle cross‑sections corresponding to the tenth rib of fifteen Lidia bulls, fought in Pamplona during the San Fermin festivities of 1997. The amount of intramuscular fat was expressed in percentage as the ratio of intramuscular fat area to total Longissimus dorsi cross‑section area. The intramuscular fat values of Toro de Lidia meat ranged from 0.6 to 4.4 p. 100, and the mean value was 1.5 p. 100. A correlation between this percentage and fat flecks size and number was observed. Therefore, the image analysis technique can be considered as a fast and objective method to quantify the degree of meat marbling. On the other hand, the results suggest that compared to other breeds of cattle, the meat of the Toro de Lidia is a lean meat, with low degree of marbling.