OBJECTIVE To determine capillary blood flow measurements in eyes with branch retinal vein occlusion using a scanning laser Doppler flowmeter. METHODS Retinal capillary blood flow in branch retinal vein occlusion areas and corresponding ipsilateral nonbranch retinal vein occlusion areas, 11 equivalent areas of the contralateral fellow eye of 12 consecutive untreated branch retinal vein occlusion patients, and 16 eyes of 11 age-matched normal control subjects were measured with scanning laser Doppler flowmetry. A template consisting of eight squares, each with a field of 100 x 100 microm (10 x 10 pixel) with space interval of 500 microm equidistant horizontally and vertically was used to obtain blood flow measurements in all subjects. Mean blood volume, flow, and velocity were obtained by averaging the mean values measured in each field. We avoided measurement over large retinal vessels to prevent the aliasing artifact of blood cells from moving faster than the sampling frequency. RESULTS Branch retinal vein occlusion areas have significantly decreased microvascular blood volume (P = .0009), flow (P = .02), and velocity (P = .016) compared with ipsilateral nonbranch retinal vein occlusion areas in the same eye. Branch retinal vein occlusion areas also have decreased blood volume (P = .001), flow (P = .0042), and velocity (P = .0044) compared with areas of contralateral fellow eyes of branch retinal vein occlusion subjects. Branch retinal vein occlusion areas have significantly decreased blood volume (P = .0012), flow (P = .008), and velocity (P = .02) compared with age-matched normal areas. CONCLUSIONS Average retinal blood volume, flow, and velocity in areas of branch retinal vein occlusion are significantly lower than in healthy retinas. The ability to noninvasively measure hemodynamic changes in the retinal capillary bed may be relevant to development of new therapies for retinovascular disease.