  Fermi gases with repulsive interactions are characterized by measuring their
compressibility as a function of interaction strength. The compressibility is
obtained from in-trap density distributions monitored by phase contrast
imaging. For interaction parameters k_F a > 0.25 fast decay of the gas prevents
the observation of equilibrium profiles. For smaller interaction parameters,
the results are adequately described by first-order perturbation theory. A
novel phase contrast imaging method compensates for dispersive distortions of
the images.

Quantum Gases