General design equations are derived from one-dimensional energy balance equations for gas-cooled current leads of high temperature superconducting (HTSC) material. The equations are solved to evaluate general characteristics for cooling with a laminar flow gas. General characteristics arranged in the design chart are applicable to the design of current leads with a wide variety of geometrical dimensions. Thermal runaway in the case of accidental stoppage of the cooling gas and the transition to the normal state of part of the current leads is analyzed. The current leads optimized under the condition of self-sustained cooling are usable in a refrigerator cooling system, almost minimizing the total refrigerator load.