A novel dialysing seton made from haemodialysis tubes was implanted into eleven rabbit eyes to establish its biocompatibility. The animals were observed for up to 67 days after implantation. The cannulae were well tolerated clinically. Tissue obtained at seven different time periods was studied by light and electron microscopy and showed only a mild inflammatory reaction of the same grade as or less than that surrounding nylon sutures used to close the scleral trapdoors. The eye containing the seton had consistently lower intraocular pressure compared to the sham-operated fellow eye for up to 24 days. This effect declined over the ensuing five weeks.