OBJECTIVE Previous methods for reconstructing semilunar valves have been characterized by lack of precision and reproducibility and, with one exception, the use of unsuitable biomaterial. A new method combines precision with simplicity to reconstruct aortic and pulmonary valves with lightly tanned autologous tissue supported by the annulus of the native valve. Essential components include sizing based on distance between adjacent commissures, cutting a seamless, size-specific trefoil-shaped pattern of tissue with a tricuspid orifice, temporary mounting of the pattern on disposable formers, and suturing with continuous or interrupted monofilament suture to join the autologous tissue pattern with the valve annulus. METHODS The tissue pattern is cut and mounted on forming devices that enable the implanting surgeon to visualize the orientation clearly, and perform repair accurately and rapidly. One, two or three leaflets can be reconstructed. The forming and cutting devices are discarded when reconstruction is complete. Diseased valves can be reconstructed in no more time than is required for replacement with a prosthesis of any type. Advantages of the method include preservation of full effective orifice area, lack of need for any foreign body other than the sutures used for reconstruction, and the use of non-immunogenic autologous tissue known to be durable and resistant to calcific degeneration. Contraindications include heavily calcified annulus that cannot be satisfactorily debrided, bicuspid anatomy, or a significantly asymmetric annulus. RESULTS Pulmonary valve reconstructions have been performed in four juvenile sheep by this method. Three animals survived five months; there was one operative death due to non-valve related causes. CONCLUSIONS Semilunar valve reconstruction with autologous tissue can be simple, precise, and reproducible.