Abstract: A monolithic silicon nitride radome structure having a forward portion, an after portion and a transition portion therebetween, is provided. The forward portion has a density of about 0.75 to 1.0 g/cc, the after portion has a density of about 1.6 to 2.0 g/cc and the transition portion has regions of increasing density, from forward to aft, each region having a greater density than the preceding portion or region. Also provided is a method for manufacturing the above-described radome structure which comprises filling and compacting a series of formulations consisting essentially of particulate silicon, silicon nitride and a fugitive pore-forming material into a radome mold, removing the shaped compact from the mold, subliming the pore-forming material from the compact to form a porous compact structure, and reacting the porous structure with nitrogen to convert the porous structure to an identically shaped radome structure of .alpha.-silicon nitride whiskers.