Waxy casts appear as cylinders of smooth, highly refractive material. They are yellow, homogeneous and their ends may be square or broken off. Cracks may occur within the cast, giving it a segmented appearance. Waxy casts are believed by some to be the final stage of degeneration of the fine granules of granular casts. Since the granules need time to degrade, this finding implies localized nephron obstruction.

Waxy casts are seen in chronic renal failure, and acute and chronic renal allograft rejection.

Unusually broad waxy casts are known as renal failure casts. These very broad casts are created in the dilated tubules seen in end-stage renal disease.