The effects of natural convection on the solidification of water on a cooled horizontal cylinder symmetrically placed in a square enclosure has been experimentally investigated. The two side walls of the enclosure were maintained at a uniform temperature that was higher than the freezing temperature of water while the lower wall of the enclosure was essentially adiabatic. The water had a free surface. The water was initially at rest and at a temperature that was above its solidification temperature. The shape of the ice/water interface was measured at various times after the cylinder was cooled. The flow patterns in the water were also studied and the mean heat transfer rate from the cylinder was measured in the final steady state. Tests were undertaken with various hot wall temperatures up to 15°C, the cylinder wall temperature in all tests being about -6°C.