  We consider the evolution of perturbed cosmological spacetime with multiple
fluids and fields in Einstein gravity. Equations are presented in gauge-ready
forms, and are presented in various forms using the curvature (\Phi or
\phi_\chi) and isocurvature (S_{(ij)} or \delta \phi_{(ij)}) perturbation
variables in the general background with K and \Lambda. We clarify the
conditions for conserved curvature and isocurvature perturbations in the
large-scale limit. Evolutions of curvature perturbations in many different
gauge conditions are analysed extensively. In the multi-field system we present
a general solution to the linear order in slow-roll parameters.
