Appreciating an imcomplete understanding of the pathogenesis of cauliflower ear, an experimental study was designed to demonstrate the pathophysiology of this deformity. The investigation was conducted in 2-month-old rabbits. In one ear a collection of blood was placed under the raised perichondrium which was then sutured back in place and the skin closed. In the other ear an equal amount of blood was deposited between the intact perichondrium and skin. In the first study new cartilage developed under the perichondrium, but in the ear in which the blood was left above the surface of the perichondrium-covered cartilage, complete resorption of the clot occurred. The cauliflower ear was thus shown to be generating cartilage, arising from a layer of raised perichondrium which was further stimulated by a sero-sanguinous medium. The subperichondrial hematoma was extensively invaded by chondroblasts within 2 weeks, and over a period of 4 weeks the new tissue gradually changed into more mature cartilage. It was a consistent finding that the separated perichondrium retracted, thus causing the original cartilage to rise and buckle over the hamatoma, similar to the picture observed in the human pathology.