Effectiveness of initial treatment of aspirin (ASA) overdosage was evaluated by comparing treatment with activated charcoal (AC) to treatment with gastric lavage in combination with AC. Dogs were used as subjects in four experimental groups. All subjects were administered an overdose of 500 mg/kg of ASA. Treatment was performed 30 minutes later on all groups except controls. Treatment with AC alone resulted in a 17% reduction (P greater than .05) of peak plasma salicylate levels compared with controls. When lavage preceded administration of AC, a 37% reduction (P less than .05) occurred. There was a 48% reduction (P less than .025) in plasma salicylate levels when lavage was preceded and followed by administration of AC. This study demonstrates that gastric lavage in combination with AC is more effective in reducing ASA absorption than AC given alone.