An inert matrix to control the release of tramadol HCl was prepared using glyceryl behenate as a matrix-forming agent. The matrices were prepared by either direct compression of a physical mixture of the drug and the matrix-forming agent or by compression of granules prepared by hot fusion of the drug and the matrix-forming agent. The hot fusion method was found to be more effective than compression of physical mixtures in retarding the release of the drug from the matrix. Drug release was adjusted by using release enhancers, such as microcrystalline cellulose and lactose, and the results showed that higher release rates were obtained using lactose. However, the release of the drug was independent of the compression force and the pH of the dissolution medium. This study showed that glyceryl behenate is an appropriate waxy material that can be used as a matrix-forming agent to control the release of a water-soluble drug such as tramadol HCl.