The practicality of obtaining significant information about profiles of Brunt-V¿is¿l¿ frequency from surface observations of internal waves is investigated. The inversion method investigated uses a three-dimensional Fourier transform (two spatial and one temporal) to determine the dispersion relations of the internal-wave modes and Abel transforms to estimate those aspects of the Brunt-V¿is¿l¿ frequency profile to which internal-wave dispersion relations are sensitive. If classical Fourier transforms are used to estimate the modal dispersion relations, observations over a 200-km square region for 17 hours would be necessary to obtain about a 15% error for one profile. However, if nonlinear methods, such as maximum entropy, could be extended to three dimensions, it might be practical to obtain significant information about profiles of Brunt-V¿is¿l¿ frequency by observing a 40-km square region for only 3 hours. This technique cannot be used when there are no significant surface manifestations of internal waves, such as during rough seas or when a significant mixed layer is present. The ambiguity of the inversion is increased when the Brunt-V¿is¿l¿ frequency profile has multiple maxima. ¿ American Geophysical Union 1995