The relative contributions of the fundamental mechanisms accounting for the enhanced heat transfer in nucleate boiling are difficult to quantify analytically or experimentally. A comprehensive model was developed that permits some accurate insights into this problem. An essential feature involved the numerical mapping of the complicated geometry to a plane where the bubble and wall boundaries lie along constant coordinate lines. The results show that microlayer evaporation accounts for 87 percent of the enhanced wall heat transfer during saturated boiling of water at 1 atm and 8.5 K wall superheat. In contrast, enhanced convective effects were essentially nonexistent during growth and minimal following departure. The analysis predicts an extremely nonuniform thermal boundary layer around the bubble, and shows that the wall thermal boundary layer regenerates almost immediately following departure.