A liquid hydrogen bubble chamber with useful volume 6¼×2¾×3 inches has been built which is expanded by a piston operating in the liquid hydrogen. Temperature control is provided by regulating the pressure in the hydrogen reservoir. Satisfactory tracks have been obtained with maximum expansion ratio of 3%, expansion time of about 5 msec, and chamber temperatures from 25.3 to above 27°K. Photographs have been taken with time delay between particles passing through chamber and light flash of 0.05 to 2.0 msec.