A rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00–10.0 µg ml^–1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing drugs. The results obtained for the assay of commercial pharmaceutical preparations compared well with those obtained by a reference method and demonstrated good accuracy and precision.