The slip history of the Izmit earthquake is investigated by jointly inverting SAR and teleseismic data with a multi-segment, variable-slip, finite fault model. Surface offsets are used as an added constraint. The highest slip values (5 to 7 m of right-lateral displacement) are associated with a strong central asperity surrounding the hypocenter. The bilateral breaking of this main asperity, which lasted about 10 sec, dominates the source time function. From the G¿lc¿k-Izmit area to Lake Sapanca, a relatively good correspondence is observed between slip at depth and at the surface, but farther to the West and to the East slip tends to be confined to the near surface. Slip in the easternmost part of the rupture (D¿zce segment) is not well resolved. Our analysis finds the InSAR and teleseismic data to be compatible and complementary. This study shows the potential of the joint inversion of both data sets for a rapid determination of the spatio-temporal history of large earthquakes. ¿ 2000 American Geophysical Union