In horizontal and extended reach drilling, a large frictional drag may occur If the pipe buckles laterally or into a helical shape, additional lateral contact force, LCF, is developed between the pipe and the wellbore wall, increasing the drag force. This paper presents the results of an experimental study of the lateral contact force between the drill pipe and the wellbore wall, for helical pipe configuration. Comparison of the experimental results with the current analytical models is also presented A horizontal well was simulated using a 2-in-dia hole 86-ft long and three different sizes of pipe. Two different techniques were used to measure the lateral contact force. Results from both techniques seem to be in good agreement. The comparison with the current analytical models shows that higher values are predicted The results will find application in directional drilling, horizontal drilling and coiled tubing operations. [S0195-0738(00)00603-8].