A collisionless kinetic ballooning-mode equation, which includes the full ion finite-Larmor-radius (FLR), the magnetic-drift, and the trapped-electron effects, is derived and investigated for a large-aspect-ratio, circular-flux-surface equilibrium in the frequency regime, ωbi, ωti<ω<ωbe, ωte. The finite-Larmor-radius effects can reduce the growth rate, but do not stabilize the ballooning modes due to the destabilizing influence of the ion-magnetic-drift resonances. It is, in general, incorrect to simulate the FLR effects by employing the often used FLR-modified MHD model for (kθρi)2⪆0.1 and n⪆0.1, where kθρi is the ion FLR parameter and n = Ln/R measures the magnetic-drift frequency. The trapped electrons have a stabilizing effect due to the reduction of the destabilizing circulating-electron parallel-current perturbation. For a typical tokamak aspect ratio, the critical β can be improved by 40%.