It is reported here, for the first time, that high quality, large single crystals of [(18C6)K][Cd(SCN)(3)] can be grown from aqueous solution via evaporation or temperature lowering techniques. The crystal of [(18C6)K][Cd(SCN)(3)] exhibits efficient second order nonlinear optical effects (as demonstrated by second harmonic generation) and has a wide optical transparency range from 220 to 3300 nm, covering continuously the entire near-ultraviolet, visible, and near infrared spectral regions. Published by Elsevier Science B.V.