The Townsend primary (&agr;) and secondary (&ggr;) coefficients and Paschen curves for neon, krypton, and their mixtures are reported. The primary coefficient was determined by measuring the variation in the luminous flux in a self‐sustained Townsend discharge between two parallel‐plate nickel electrodes spaced 21.5 mm apart. The values for the reduced primary coefficient &agr;/p0for Ne and Kr are about 10–20% lower than the published values obtained by the classical method of Townsend. The &agr;/p0values for Ne agree with results of previous work using the same luminous‐flux method. The ionization efficiency function &eegr; (&eegr;=&agr;/E, whereEis the electric field) for a Ne‐Kr gas mixture has a maximum value (0.0040 V−1) for Ne admixed with 0.1% Kr.