The paper presents a derivation of Nyquist sampling requirements for the polar grids in some bistatic time-domain algorithms. The derivation is based on an airborne bistatic system with general bistatic geometry. The Nyquist sampling requirements are shown to be the functions of operating radar frequency, transmitter and receiver subaperture lengths, and bistatic geometry. How to decide the Nyquist sampling requirements for different bistatic geometries and the relationship between the Nyquist sampling requirements in the monostatic and bistatic cases are also addressed in the paper. The derived Nyquist sampling requirements is examined with the bistatic CARABAS-II like data.