A novel abnormality of intramural coronary arteries has been recently described in allograft cardiac biopsies. Three-dimensional (3-D) models of these abnormal arteries have now been constructed from serial histological sections of diagnostic post-transplant endomyocardial biopsies. These revealed that there was an interlacing meshwork of longitudinal smooth muscle bundles in abnormal arteries. In addition, the lumen and external surface of these arteries were irregular. This contrasted with reconstructions of normal control arteries in the same sections, which were smooth and straight. This elucidation of an unusual abnormality suggests that 3-D reconstruction of arteries in forceps biopsies may be a useful technique.