In addition to wide band thermal noise, metal-electrolyte interfaces generate spontaneous voltage fluctuations of electrochemical origin. They range in duration from less than 100 msec to more than several seconds. Special activities are spikes and semi-periodic oscillations. Amplitudes are usually below 1 mV on macroscopic specimens. Similar fluctuations can also be mechanically induced. Results are documented from silver, platinum and stainless steel. Fluctuations were also observed with copper, brass, aluminum, monel, solder, mercury, carbon and degenerating Ag−AgCl electrodes. Several examples of artifact in biological data are discussed.