Abstract: A composite diaper is configured for use in conjunction with a spica cast having cast interior and outer surfaces and a waste-elimination opening defined therein for facilitating the wearer's elimination of bodily waste. The composite diaper comprises mutually attached inner and outer diaper-panel sets. The inner diaper-panel set includes front and rear inner panels, and the outer diaper-panel set includes front and rear outer panels. The front and rear inner panels are configured for insertion through the waste-elimination opening and disposition between the cast interior surface and, respectively, the wearer's abdomen and buttocks. The front and rear outer panels are configured for drawing up and fastening to one another over the cast exterior surface, thereby retaining the inner diaper-panel set in position and, depending on the specific configuration, providing a secondary layer of bodily-waste absorbency and containment and/or a layer of protection against waste leakage to the cast exterior.