Tissue engineering (TE) of the cardiovascular system, including heart valves, is an innovative concept. An important aim is to generate fully functional heart valves for patients with cardiovascular problems. The paper by Sarraf and colleagues in this issue of Heart, Lung and Circulntion reviews the development of this newly emerging multidisciplinary field. The paper gives a lengthy overview of various aspects of tissue engineering; however, we feel that there are a few issues that should have been discussed in more depth by the authors. These are mainly related to the engineering and biomaterials aspects of tissue engineering. Tissue engineering of cardiac moieties often involves formation of functional tissue on the basis of a bioresorbable scaffold. The scaffold provides a temporary biomechanical structure until the cells produce their own matrix proteins. The structural integrity and biomechanical profile of the TE constructs ultimately depend on this matrix formation. For this reason we feel that it is important to describe the biomaterials commonly used for scaffolds (not only polyglycolic acid) and common fabrication methods for a more comprehensive review. Review articles that cover this subject1-3 should at least be briefly referred to, as this is one of the major problems facing tissue engineering of heart valves. It should also be mentioned that there are important and challenging issues in the design and manufacture of biomaterials for cardiac use and in the mechanical structure of cardiac tissues such as valve leaflets or the compliant aortic wall, and the interaction of these with the fluid flow. At Swinburne University, we focus upon the modelling and fabrication of 3-D scaffolds using the Fused Deposition Modelling (FDM) process and subsequent in vitro modelling of the seeded constructs. FDM, developed by Stratasys Inc. (Berlin, Germany), is one of the most established rapid prototyping processes for fabrication of physical models under computer control directly from a computer-aided design 3-D solid model of an object. It uses a layer-by-layer deposition of molten thermoplastic through a nozzle fitted in a liquefier head. The FDM process can build solid as well as honeycomb style porous models of uniform porosity and structure suitable for scaffold applications in tissue engineering. We agree that by simulating physiological conditions in vitro, the resulting tissue engineered heart valve would have greater functional performance and maturity than a statically seeded scaffold. We also agree that the tissue engineered heart valve should ideally possess an endothelial lining to best approximate a natural heart valve. In the section hydrolytically degradable scaffolds, it is important to focus on the materials that degrade by way of hydrolysis. There is much recently published information in the literature on this subject.4-6 In conclusion, tissue engineering is an exciting new area where medicine, science and engineering meet. We can look forward to further discoveries and increasing demand for applications of tissue engineered devices in the next few years.