A multichannel analysis is introduced to constrain seismic anisotropy from the shear wave splitting of SKS and SKKS. This technique utilizes simultaneously a set of records coming from different azimuths. The splitting intensity of SKS waves, measured by the amplitude of the transverse component, depends on the angle between the back azimuth of the earthquake and the direction of the symmetry axis and on the delay time Δt between the two quasi-shear waves. It is shown that the splitting parameters can be determined from the azimuthal dependence of the splitting intensity, which is given by the first right eigenvector of the matrix containing the transverse components of all the records. Alternatively, the splitting intensity can be measured by projecting the transverse components on the radial components derivatives. Experiments on synthetic seismograms demonstrate that both approaches provide robust estimates of the splitting parameters. However, the projection approach gives measurements that are closer to the inputs and with smaller error bars, which suggests that it should be preferred when the signal-to-noise ratio is low. The new technique is applied to analyze shear wave splitting under stations BCAO (Bangui, Central African Republic) and BDFB (Brasilia, Brazil). The analysis of 75 seismograms recorded by station BCAO gives a fast polarization direction in very close agreement with the present-day motion direction of the African plate. Comparisons with the results of previous studies, obtained with other techniques and smaller data sets, suggest that some of the published measurements may be strongly biased. The main limitation of the multichannel analysis is a good azimuthal distribution of the seismicity. Maps of the azimuthal coverage were determined, and it is found that the most favorable regions to study anisotropy with SKS waves are a latitudinal band that goes from South America to Africa, the eastern part of North America, and India. ¿ 2000 American Geophysical Union