A SnO₂ transparent thin-film transistor (TTFT) is demonstrated. The SnO₂ channel layer is deposited by RF magnetron sputtering and then rapid thermal annealed in O₂ at 600°C. The TTFT is highly transparent, and enhancement-mode behaviour is achieved by employing a very thin channel layer (10–20 nm). Maximum field-effect mobilities of 0.8 cm² V-¹ s-¹ and 2.0 cm² V-¹ s-¹ are obtained for enhancement- and depletion-mode devices, respectively. The transparent nature and the large drain current on-to-off ratio of 10⁵ associated with the enhancement-mode behaviour of these devices may prove useful for novel gas-sensor applications.