Burrowing times of winter acclimated populations of Donax serra from the west and south coasts of South Africa were compared at three experimental temperatures in an effort to explain observed zonation patterns. The west coast population burrowed slower than the south coast population at 10°C and 15°C, but at the same rate at 20°C. Burrowing time decreased at increased temperatures. The burrowing rate index ranged from 5 to 14, indicating that D. serra is among the most rapidly burrowing bivalves examined to date. The results indicate no physiological adaptation of burrowing rate to tem perature between populations.