Thin sputtered tungsten films on various substrates (molybdenum or tungsten foils, quartz and glass slides) were reacted with H 2S at temperatures from 400 to 1000 °C. In general, it was found that the WS 2 crystallites nucleate from an amorphous WS 3 phase. It was established that the substrate has a critical role in determining both the reaction onset temperature and the texture. For glass substrates, the reaction to give WS 2 begins at T ⩾ 400 °C, and the WS 2 grains grow predominantly with the van der Waals (vdW) planes parallel to the substrates (in this orientation, the c axis is perpendicular to the substrate, and is designated ⊥c) at 500 °C. On quartz substrates, reaction begins only at 650 °C and the texture is predominantly vdW planes perpendicular to the substrate )this orientation is designated ‖c) below 950 °C, and exclusively ∋ texture at higher temperatures. These differences between glass and quartz are believed to be due to sites on the quartz, absent (or present to a smaller extent) on glass, which strongly bind the tungsten and WS 2. Molybdenum substrates give only the ‖c orientation even at 1000 °C, while bulk tungsten (or tungsten sputtered on tungsten) gives randomly oriented WS 2. For oxidized tungsten on quartz, reaction onset is lowered to 500 °C (compared with 650 °C for W/quartz), and predominantly ⊥c orientation is obtained at 800 °C. Exclusively ⊥c orientation was never achieved with this system, even at 1000 °C. It was found that the ‖c orientation changes to the ⊥c orientation when diffusion conditions (temperature and time) were sufficient, indicating that the latter orientation is energetically favourable.