A particularly dangerous mode of instability in confined plasmas is the trapped particle mode which is highly insensitive to magnetic shear and average favorable curvature. The study of the collisionless trapped particle mode is extended to include the effects of finite&bgr; = 8&pgr;nT / B2. It is found that the “magnetic well” dug by plasma diamagnetism is highly effective in stabilizing the collisionless trapped‐particle mode. It is found that for magnetohydrodynamically stable systems the collisionless trapped‐particle mode becomes stable when the diamagnetic well is sufficient to give all particles average favorable drift. It would appear from this result that, in general, the diamagnetic well should be an effective stabilizing agent against all nonflutelike microinstabilities.