Dipole radiation in a two‐dimensional periodic dielectric structure is studied both theoretically and experimentally in this article. For the two‐dimensional square lattice structure with dielectric cylinders, the emission power of an electric dipole in the photonic band structure is computed numerically by a combination of the plane wave method, the dyadic Green’s function, the Poynting theorem, and the triangular integration method. The theoretical results are compared with experimental measurements in a microwave frequency region. The computed radiation spectra in the photonic band structure show good agreement with the experimentally measured results. ©1996 American Institute of Physics.