We are constructing a model which aims to reproduce observational data of many kinds related to cosmic-ray origin and propagation: direct measurements of nuclei, antiprotons, electrons and positrons, gamma-rays, and synchrotron radiation. These data provide many independent constraints on any model. Propagation of primary and secondary nucleons, primary and secondary electrons and positrons are calculated self-consistently. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Our main results include evaluation of diffusion/convection and reacceleration models, estimates of the halo size, calculations of the interstellar positron and antiproton spectra, evaluation of alternative hypotheses of hard nucleon and hard electron interstellar spectra, and computation of the Galactic diffuse gamma-ray emission.