Caisson or bucket foundations are being used increasingly for offshore developments, in soil conditions ranging from soft clay to dense sands. This paper addresses the performance of caisson foundations in fine-grained calcareous soil, under combined vertical (V) and horizontal (H) loading. Results of centrifuge model tests are presented, aimed at defining the shape of the yield envelope in V-H space, and the foundation response inside the yield envelope. It is shown that the tension and (compressive) bearing capacity for the caisson are similar, and that the maximum horizontal capacity is mobilised at close to zero vertical load. Work hardening of the yield envelope due to additional penetration of the caisson is demonstrated, as is the similarity of the yield function shape at different penetrations. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.