Between January 17 and March 11, 1991, 0.15 km3 of lava erupted initially from several radial fissures and subsequently from a single fissure on the SE flank of Hekla volcano, Iceland. Hekla is surrounded by an array of control points measured in 1989 using GPS geodesy and re-measured after the eruption. These measurements indicate that the eruption was associated with a surface deflation volume of 0.1+0.08-0.04 centered on Hekla (63.995¿N+4-3, 19.69¿W+1.5-2 km). The depth to the magma reservoir is 9+6-7 km, poorly constrained due to the absence of GPS control points close to the volcano.