We inverted strong motion data for the finite source parameters of six large aftershocks of the 1999 Chi-Chi, Taiwan, earthquake to investigate seismogenic structure in Taiwan. For each event we derived a preferred model by testing different focal mechanisms, hypocenters, rupture velocities, and dislocation risetimes, as well as different combinations of stations in more than 1000 inversions. We documented how the fits between the waveforms and the corresponding synthetics deteriorated as the hypocenter and focal mechanism deviate from those of the preferred model. If the deviation in focal mechanisms and hypocenters is less than 20¿ and 5 km, respectively, we generally recovered 80% of the preferred model's synthetic waveform fit. Unlike the dislocation risetime, the rupture velocity used in the inversion had a strong influence on the waveform fits in this study. We also used the slip models to study fault geometry. Two of the aftershocks ruptured on the southern extension of the main shock slip area. One strike-slip aftershock nucleated within the basement but ruptured mainly within the overlying sedimentary strata, suggesting that seismogenic deformation in the basement can influence shallow structures. P axes of the derived models have azimuths consistent with current plate motion. Finally, GPS displacement derived from the six slip models can explain 80% of the postseismic deformation observed in the aftershock regions, indicating that studies of postseismic deformation must take into account the cumulative effects of large, shallow aftershocks.