A series of high-quality conventional and explicitly correlated second-order Moller-Plesset energies, denoted as MP2 and MP2-R12/A, respectively, was computed in a state-of-the-art attempt to arrive at the ab initio limit for the barrier to linearity of water. [O/H]-centered Gaussian basis sets as large as [19s13p11d9f7g5h3i/13s11p9d7f5g3h] were employed in the study. We find that basis functions with high orbital angular momentum quantum number (h and i) are important for highly accurate predictions of the electronic energy, even when explicitly correlated approaches are utilized. This observation is at variance with previous claims that explicitly correlated methods require basis sets saturated only to the level of f functions for spectroscopic accuracy. Our best explicitly computed value for the MP2 contribution to the barrier is -357 cm(-1). The resulting final ab initio estimate for the classical barrier to linearity of water is 11 119 +/- 15 cm(-1), in good agreement with the most recently obtained empirical value of 11 105 +/-5 cm(-1). (C) 2001 American Institute of Physics.