Abstract We compared, by transmission electron microscopy (TEM), the ultrastructure of interstitial Cajal-like cells (ICLC) in normal mammalian myocardium versus caveolin-1 null mice. TEM showed that myocardial ICLCs of caveolin-1-deficient mice retain their main ultrastructural characteristics, for example, location among cardiomyocytes, close vicinity to nerves and/or blood capillaries, specialized cell-to-cell junctions, presence of 2-3 typical processes, which are very long (several tens of micrometres), but are very thin (0.1-0.2 microm) and moniliform. However, the most striking modification of myocardial ICLC in caveolin-1 KO mice was the absence of caveolae. Beyond this main observation, three other findings could be reported: (1) the absence of caveolae in capillary endothelium, (2) persistence of (some) caveolae at the level of cardiomyocte sarcolemma or vascular smooth muscle cell sarcolemma and (3) (un)expected ultrastructural modifications such as increased thickness of capillary basement membrane and increased autophagy of several cardiomyocytes.