1 The absorption of effervescent aspirin was studied in normal volunteers of both sexes under varied conditions of activity in both fasting and non-fasting states. 2 Moderate activity resulted in no significant changes in absorption compared with that at rest. 3 In non-fasting subjects the absorption was reduced but this reduction was attenuated with time until after 60 min the plasma levels were similar. 4 There was no interaction between the resting/non-resting and fasting/non-fasting absorption.