Approximations for the frequency of the new resonance of a vapor bubble associated with evaporation and condensation are derived from the equations of ’’Vapor bubble dynamics’’ [R. D. Finch and E. A. Neppiras, J. Acoust. Soc. Am. 53, 1402–1410 (1973)]. Previous predictions of the new resonance frequency ω were obtained by numerically solving a secular equation. The purpose of the approximations is to elucidate the significant parameters; for example, the surface tension σ is predicted to greatly influence ω. When the liquid’s thermal conductivitykis sufficiently large, ω∝σ2/3 R−8/3, whereRis the equilibrium radius of the bubble; smallkgives ω∝σ2 R−4. The approximations are substantiated by comparisons with numerical results for water, nitrogen, and helium. Criteria for their use are presented. Effects of evaporation–condensation resonance on radiation pressure and extinction of sound are suggested.