Adaptive transparency is a new solution to order-independent transparency that closely approximates the ground-truth results obtained with A-buffer compositing but, like a Z-buffer, operates in bounded memory and exhibits consistent performance. The key contribution of our method is an adaptively compressed visibility representation that can be efficiently constructed and queried while rendering. The algorithm supports a wide range and combination of transparent geometry (e.g., foliage, windows, hair, and smoke). We demonstrate that adaptive transparency is five to forty times faster than realtime A-buffer implementations, closely matches the image quality, and is both higher quality and faster than other approximate order-independent transparency techniques: stochastic transparency, uniform opacity shadow maps, and Fourier opacity mapping.