Langmuir and Langmuir-Blodgett (LB) films of a family of amphiphilic fullerene derivatives, the fullerene-aza-crown ethers, have been produced. The use of high concentrations of K+ ions in the subphase leads to Langmuir films (type II) with significantly higher areas/molecule than are obtained with no ions in the subphase (type I). The type I films were transferred onto hydrophilic glass substrates and were found to exhibit second-order nonlinear susceptibilities, chi(pp)((2)), of 2.3-3.6 pm/V, the first chi(pp)((2)) values to be determined of LB films of fullerene derivatives.