  Fourth-derivative gravity has two free parameters, $\alpha$ and $\beta$,
which couple the curvature-squared terms $R^2$ and $R_{\mu\nu}^2$. Relativistic
effects and short-range laboratory experiments can be used to provide upper
limits to these constants. In this work we briefly review both types of
experimental results in the context of higher-derivative gravity. The strictest
limit follows from the second kind of test. Interestingly enough, the bound on
$\beta$ due to semiclassical light deflection at the solar limb is only one
order of magnitude larger.
