The experiment of pool nucleate boiling of water was performed on a heated silicon surface with triple artificial cavities. The existence and the significance of three effect factors, the bubble coalescence factor 'C', the thermal interaction factor 'T' and the hydrodynamic interaction factor 'H', in the mechanism of nucleation site interaction is validated by comprehensive analysis and observation. It is revealed that the interaction is classified into three regions due to effects of the three factors. (C) 2004 Elsevier Ltd. All rights reserved.