Synaptic transmission in the nervous system in general and in the retina in particular is highly sensitive to changes in extracellular pH. Alterations in the level of free protons act on calcium channels to regulate the influx of calcium, with increased concentrations of H+ acting to reduce calcium influx with consequent reduction in the amount of neurotransmitter released. It has been proposed that such changes in extracellular pH might act normally to shape the response properties of retinal neurons. In the present work, we have monitored changes in the concentration of H+ directly adjacent to retinal horizontal cells of the goldfish. Isolated horizontal cells were obtained by an enzymatic dissociation protocol employing the enzyme papain. Self-referencing pH-selective microelectrodes were placed approximately 1 µm from the plasma membrane of cells. Recording parameters were adjusted to detect rapid alterations in H+ concentration. In a number of retinal horizontal cells, we observed waves of spontaneous changes in extracellular pH, with the surface near the cell alternating between being more acidic and more alkaline than a point 30 µm distant from the cell. The oscillations were generally reduced or abolished when 100-200 µM glutamate was added to the bath. We are currently examining the hypothesis that such alterations in proton flux may be associated with alterations in membrane potential shown previously to occur in isolated retinal horizontal cells.