The deformation of a 20 m deep firn pit in the accumulation area of Kesselwandferner was surveyed over a period of 11 years. Six or seven surveying markers had been installed at each of 14 levels. The survey shows that the shear strain rate is independent of depth and the originally circular pit cross section was changed into an ellipse. In the direction of the glacier flow, the diameter was increased, the strain rate being approximately independent of depth. Transverse to the flow, however, the diameter decreased, the strain rate becoming higher as the depth increased. The vertical strain rates responsible for thinning of firn layers decrease with depth.