The recently reported dramatic population increases (outbreaks) of the coral-eating crown-of-thorns starfish, Acanthaster planci, which have damaged many reefs in the Indo-Pacific, are ending (1), but questions remain about the factors that affect Acanthaster distribution and densities. For example, the narrow temperature tolerance (26° or 27° to 30° or 31°C) reported for Acanthaster's larval development (2) is problematic because Acanthaster occurs where temperatures do not rise into this range (3, 4). We have further examined some temperature relationships in Acanthaster's early development. Cleavage proceeded normally over a range of about 10°C but specific limiting temperatures depended upon the geographic source of the parents or their recent history of temperature exposure. Hatched, swimming gastrulae continued normal development to bipinnaria throughout a temperature range of 13°C. These results indicate that the narrow developmental temperature tolerances reported earlier for Acanthaster do not apply to all early developmental stages, and they add to the list of larval adaptations that can facilitate dispersal of Acanthaster larvae and propagation of outbreaks.