Since the large third-order optical nonlinearity of organic metal (alpha) -(BEDT-TTF)2I3 was reported by Huggard et al. in 1987, the nonlinear optical properties of organic metals have received great attention. New synthetic routes for metal-dithiolene complexes were developed in the last decade and several of the complexes which have a TTF-analogous structure proved to be good electrical conductors. THG activities of solutions of some of these metal-dithiolene complexes were measured by using a THG Maker fringe method. For example, the (Chi) (3) value of a 0.2 wt% DMF solution of Ni(dmbit)2TBA at 0.1 mm thickness was measured as 7.2 X 10-14 esu by using 1,319 nm Nd:YAG laser light. In this measurement the (Chi) (3) value of 2.8 X 10 -14 esu for the SiO2 glass was used as a reference. From this measurement a (Chi) (3) value as large as 3.6 X 10-11 esu is predicted for the neat compound.