The growth of In2S3 and InS by vacuum evaporation of indium metal on the surface of molybdenite has been observed in the initial stage of film growth. By the increment of In2S3 particle size, InS was also produced. By the increase of the film thickness to more than 20 nm, indium crystal predominately grew. The topotactic relations among the substrate and sulfide are as follows: (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 1 1](In2S3) or (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 0 0](In2S3).