Radiation‐field‐dependent frequency shifts arising in atomic‐beam spectroscopy are treated theoretically and experimentally. Shifts due to fundamental and unavoidable interactions between the radiation field and the atoms comprising the beam are distinguished from those due to various ``apparatus effects.'' Precise measurements of frequency shifts are made for a cesium beam experiencing Ramsey‐type excitation. For the magnetic‐field‐sensitive transitions (F, MF) = (4, ±1) ↔ (3, ±1), the magnitude of the shifts is about 1 part in 1010of the resonance frequency value, per milliwatt variation of input power to the radiation field. The shifts vary with input intensity in a nonmonotonic fashion and are shown to result from nonuniformity in the static magneticc‐field of the apparatus. Much smaller shifts of about 5 parts in 1013per milliwatt are observed for the magnetic‐field‐insensitive transition (F, MF) = (4, 0) ↔ (3, 0). The major features of these shifts are shown to arise from spectral impurities in the radiation exciting the transition and a small phase difference between the pair of separated radiation fields. The bearing these results have on evaluating the accuracy of an atomic beam frequency standard is discussed.