The normal distribution of the retinal blood flow in the cat eye was modified by photocoagulation to part of the territory supplied by a major arteriole, or by occluding a branch. Volume inflow to the treated territory was reduced, and there was also a reduction of linear flow and, to a less extent, calibre in the parent vessel. Branches of the parent vessel supplying untreated territory showed marginal increases of volume inflow. An autoregulatory effect appeared to be operative. The relevance of these findings to clinical panretinal photocoagulation is discussed.