Reflection seismic measurements were carried out during 1985 in the area of the Siljan impact structure of Sweden. A total profile length of 80 km was shot to get a clearer picture of the subsurface geometry of impact structures and the process that formed them than could be obtained from surface observations or theoretical modeling studies. Standard stacked sections have been interpreted in terms of current impact models. The transient crater diameter is found to be approximately 22 km, considerably smaller than current estimates based on interpretation of surface geology. The structural uplift is estimated to be 3 km at the 5- to 8-km level, and the material flow necessary to support the uplift is mainly horizontal ¿ American Geophysical Union 1987