Recently developed plasma potential diagnostic techniques which employ emissive probes are discussed. Using these techniques it is shown that it is possible to determine the plasma potential in plasma densities of <104 to 1013 cm−3, neutral pressures of <10−6 to 1 Torr, ion temperature ranging from 0.1 eV to 1 keV, and electron temperature from 0.1 to 150 eV. The techniques include measurements of the inflection point of the probe’s I–V characteristic in the limit of zero electron emission, differential emissive probes in which a feedback circuit compares two probes with different emission, self-emissive probes in which plasma bombardment provides the probe heating, secondary emissive capacitive probes for which secondary electron emission coefficients are greater than 1.0, and current biased probes.