Cold-water corals are known to grow much slower than their tropical counterparts. However, this assumption is mainly based on laboratory measurements exposing specimens to conditions that differ from their natural environments. The cosmopolitan scleractinian Desmophyllum dianthus forms dense banks below 18min northern Patagonia, Chile. So as to measure in situ growth rates of this cold-water coral, specimens were collected from two sites, weighed and deployed on holders in their natural headlong orientation at the respective collecting site. Corals exhibited a calcium carbonate (CaCO3) mass increase of 5.44+/-3.45 (mg (cm2 projected calyx area)^-1 day^-1) after 2 weeks, equivalent to a mass gain of 0.25+/-0.18 s.d. % day^-1. In comparison, D. dianthus specimens from the same collection sites maintained in an on-site flow-through aquarium system showed lower growth rates that were third of the in situ rates. In situ CaCO3 precipitation of D. dianthus extrapolated for 1 year (kg m^2 year^-1) displays the same order of magnitude as reported for massive growing tropical scleractinians, e.g. Porites sp.