The weakly bound long-range potential curves between a highly excited alkali atom M-*(n(e)s) and a ground state alkali atom M(n(g)s) are calculated using simple but reasonably accurate models for long-range dispersion and exchange interactions for all homonuclear and heteronuclear combinations. For K-2, where experimental results are available, the agreement is quite good (binding energies of observed vibrational levels within similar to10%). We find that at least a zero-point vibrational level occurs for n(e)-n(g)less than or equal to12. (C) 2004 American Institute of Physics.