Integrating tomography in the design of future experiments requires knowledge of the information content of this type of data. The case of mesoscale observations is examined here. The evaluation of the performances of tomography, as the only data type available, is done by simulating acoustic transmissions in a quasi-geostrophic model during a period of 106 geophysical days. A linear inversion is then applied to recover the stream function field. The linear hypothesis is validated for that particular scale and type of oceanic perturbation, as is the robustness to erroneous data. The full three-dimensional stream function fields are reconstructed. Information brought by tomography varies according to the mode: the first baroclinic mode is well estimated, the barotropic mode is partially estimated (only one component of the current is felt), and higher modes are not resolved. The relative vorticity is assessed with horizontal resolution at the scale of the elementary cells defined by the tomographic array; it is compared to direct triangular computations. The original contribution of tomography is in the simultaneous time and space dimensions, complementary to the classical point measurements. ¿ American Geophysical Union 1992