The standard V-A theory of terrestrial beta decay is reviewed. Modifications required for treatment of negatron emission, positron emission, and electron capture under stellar conditions are discussed. Ionization states, population of nuclear excited states, and lifetimes against the appropriate beta decay processes are calculated for 36 beta-active nuclides lying on or near the canonical s-process path, for a range of temperatures and densities characteristic of the shell helium burning phase of red giant stars. An example is given showing the applicability of these results to determinations of the time scale of the s-process.