It is commonly asserted that high-order n-body terms are energetically insignificant. In particular, for homogeneous water clusters it has been assumed that the n-body corrections are negligible beyond n = 4, or possibly n = 5. (Higher-order terms undoubtedly persist in ion-water clusters. ) A careful analysis of this assertion in large (N 20) water clusters has been hindered by intractable combinatorics, but should now be feasible and we hope to report on this in due course. For now, we note that that terms beyond n = 5 in (H 2 O) 20 clusters converge to a constant, nonzero error [Fig. ]. We ascribe this constant offset to the combined effects of BSSE and perhaps some residual error due to the supersystem correction. This analysis suggests that for N = 20 monomers, MBE(n) does indeed converge at the n = 5 level at worst, and perhaps sooner, if higher-quality basis sets were to be employed. Others have suggested that five-body terms in neat water clusters are BSSE artifacts that disappear in the complete-basis limit. The present results certainly do not preclude that possibility, which we plan to explore in future work.