  We find the general behaviour of homogeneous and isotropic cosmological
models in some fourth-order theories of gravity. Explicit, exact, general
solutions are given for both empty universes and those filled with a perfect
fluid. For the vacuum case, solutions are found with closed, open and flat
geometries, whilst the perfect fluid solutions are all spatially flat. Both
early and late-time limits are studied, and attractor behaviour towards simple
power-law expansion is identified. Multiple solutions to the same theories,
with the same matter content and topology are found. It is shown that these
solutions exhibit great variety in their evolution.
