A membrane protein (FAT) homologous to CD36 has recently been implicated in the binding and transport of long-chain fatty acids (FA). Expression of this protein in rat heart, skeletal muscles and in isolated cardiac cells was studied. Changes in expression during development of the heart were also examined. Expression of FAT was compared to that of the cytoplasmic fatty acid-binding protein (H-FABP) to determine whether coexpression, indicative of related biological functions, could be demonstrated. FAT and H-FABP mRNAs showed a similar muscle tissue distribution and similar cellular localization in the heart. During development, heart mRNA levels for both proteins were upregulated in the same way. In conclusion, expression of FAT and H-FABP in muscle tissues and cell-types with high FA metabolism and the upregulation of mRNA levels associated with heart development, when FA utilization increases, support the suggested role of both proteins in FA metabolism.