A robot foot may tip-over when it is subjected to forward as well as lateral turning moments. In this thesis boundary element method is used to perform foot-to-ground elastic contact analysis. The procedure is iterative, and makes use of both displacement and stress contact conditions, namely, no interpenetration, and compressive normal stress. Contact region and stress distribution in the region may be determined in the analysis. In this thesis the ground is rigid while the foot is elastic. A normal force, together with forward and lateral turning moments, are applied to the foot. The critical turning moments causing tipping-over may be determined. The critical moments for a semi-circular foot are compared to the moments for a rectangular foot.