The ciliary body is an important component in the tissue interactions that occur during the normal development of the eye. The ciliary epithelium is induced by the lens from the rim of the optic cup and probably reciprocates by determining the position of the germinative zone of the lens. The ciliary epithelium is also likely to induce the differentiation of the ciliary muscle and stroma from the surrounding neural crest-derived mesenchyme. Intraocular pressure plays a major role in co-ordinating the growth and morphogenesis of many ocular tissues, including the ciliary body. A central question addressed in this review is whether this pressure is generated by the early activity of the ciliary epithelium or by the growth and osmotic activity of the vitreous body.