Sonograms of Longissimus dorsi muscle (LDM) area were taken before slaughter on the last thoracic vertebra by an Aloka SSD-500. Three sonograms of each bull were taken with 60, 65 and 70% ultrasound intensity. A digital image of the LDM area was obtained on the last thoracic vertebra. Intramuscular fat content was detected by an Infratec 1265 - Meat Analyzer. The grey value of the sonogram measured by computer image analysis significantly correlated with the content of IMF, r=0.78 for Slovak Simmental, and r=0.60 for Holstein bulls. Area proportion of marbling determined on images obtained by computer image analysis (MARB) correlated significantly with IMF, r=0.65. This correlation was only significant for Slovak Simmental bulls. The obtained results suggest that prediction of intramuscular fat in meat is possible using the technique of ultrasound and computer image analyses of live animals. Further investigation is needed to improve measurement precision and to validate applicability among a wide variety of cattle breeds.