Abstract: The use of cone penetration test results to evaluate the capacity of single piles, referred to as in-situ test-based design method in China, is restricted largely to precast concrete piles. This method may not be applicable to small-displacement steel pipe piles which further encounters the problem of soil plug. Attempts have been made overseas for the design of steel pipe piles such as the ICP and UWA methods and more recently the HKU method developed by the authors. The three methods have similar theoretical background, and they all correlate the base and shaft resistances to the cone tip resistance. The predicted capacities of full-scale test piles, however, differ significantly. Such uncertainty is associated with several important factors such as separate/combining evaluation of the annulus and plug resistances, proper considerations of influence zone and friction fatigue and, utilization of plug indices to include the effects of partial plugging and soil displacement due to driving.