Volcanos at Rabaul Caldera, Papua New Guinea, erupted large volumes of ash and pumice during September 1994. Prior to the eruption, coral reefs flourished in and around Rabaul Harbour, with live coral cover typically around 50%. Following the eruption, most areas of reef flat within the harbour were completely buried by ash. By August 1996, Pocillopora corals had extensively recolonised hard surfaces in the ash field covering the reef flat. Recolonised surfaces included volcanic boulders, tree stumps and dead coral matrix protruding from the ash field Fig. 1). We recorded coral densities up to 630/m2 on these surfaces. Coral size ranged from a few millimeters up to 10 cm in diameter, indicating an extended recruitment regime. No corals had recruited to the unconsolidated substratum of ash. Coral mortality from the eruption was also high on steep reef slopes in the harbour. However, in contrast to the reef flat, recovery on the slope was largely from regrowth of existing corals. Ash retention on slopes was substantially less than on the reef flat, thereby enhancing survival of corals. Reefs outside the harbour exhibited much lower mortality, and recovery by regrowth of existing colonies predominated.