In vivo cannulation of retinal blood vessels has not been reported but would be useful in exploring local vascular parameters and new treatment modalities. We developed a microsurgical technique for cannulating rabbit and cat retinal vessels, using glass micropipettes with curved shanks made from standard capillary tubing. The micropipette was held by a micromanipulator, which was fitted with a fiberoptic sleeve for intraocular illumination and for micropipette tip protection during insertion through the sclera. Direct aspiration from and injection into retinal blood vessels were possible.