This paper describes the design and performance of a plaque aimed at delivering hot-water hyperthermia to intraocular tumors. The plaque transfers heat into the tissues via conduction. Maximum temperature cannot exceed inflow water temperature. The high water flow rate provided by the hyperthermia unit guarantees an excessive power output at a constant temperature level, resulting in a homogeneous temperature distribution in the tissue. Heat distribution over the plaque surface was shown to be uniform. System performance has been studied on enucleated human as well as on living rabbit eyes. Thermal mapping was done in two and one planes, respectively, and the spatial distribution was calculated. Results promise therapeutic temperature levels to a depth exceeding 10 mm.