The bioavailability of a new enteric-coated tablet of aspirin (Ecotrin, Smith, Kline and French) was evaluated after single doses to eight volunteers. One tablet was administered to each subject on four occasions--twice after a light breakfast, once after a heavy breakfast and once after pretreatment with metoclopramide. The study utilized non-invasive techniques. The rate of absorption of aspirin was estimated by the time course of concentrations of salicylate in saliva, while the total bioavailability was determined by the recovery of total salicylate in urine. The urinary recovery of aspirin from all 32 trials was 575 +/- 25 mg (mean +/- standard error), representing 89% +/- 4% of the administered dose. The different treatments did not significantly alter the urinary recovery. The absorption of aspirin from the enteric-coated tablets was delayed and slow. Absorption was retarded by a heavy meal and hastened by pretreatment with metoclopramide. The effect of metoclopramide is consistent with the release of aspirin in the small intestine. Overall, the single-dose tests indicated satisfactory functioning of the enteric coating.