We use a nonlinear inversion approach for determining source parameters of the Fucino Ms=6.9 earthquake that occurred along central Apennines, Italy, in 1915, taking into account both near-field surface deformations and far-field first-motion polarities. This event was one of the most destructive in Italy this century, causing over 30,000 casualties. Altitude and leveling measurements were performed before (1862) and after (1917) the event, along a circular route consisting of 18 benchmarks. Polarities of first arrivals do not constrain a unique fault-plane solution, while the one obtained by inverting geodetic data, with relevant constraints provided by neotectonic data, disagrees with P wave polarities. Our joint inversion, based on a robust fitting technique, has resulted in only one well-defined solution, satisfying geophysical data as well as surface-faulting distribution and paleoseismological information. ¿ 1998 American Geophysical Union