The UV-and-x-ray double-resonance absorption process in 1 mm tryptophan grains was studied. The excited molecular density can be obtained by the use of a three-state model for UV absorption. The dependence of the x-ray transmittance on the UV-laser photon flux using was investigated using the x-ray absorption cross sections obtained by a calculation based on the atomic Hartree-Slater method. It was found that x-ray absorption is increased markedly by the use of a 5-ns UV pulse with a peak photon flux of ~1025 photons cm-2 s-1. Furthermore, the feasibility of x-ray microscopy using double-resonance absorption is considered. It is expected that the images of particular molecules can be obtained selectively with a good signal-to-noise ratio.