The concentrations of acetaminophen in human plasma were determined by RP-HPLC after administration of a single oral dose of 1000 mg acetaminophen oral drop or tablet to eight normal male volunteers in a crossover study. The concentration vs time curves of acetaminophen all fitted the two compartment model. The Cmax in oral drop and tablet were 11.23 +/- 0.93 and 8.79 +/- 0.93mg/L, respectively; Tmax were 0.86 +/- 0.08 and 1.48 +/- 0.39h; T1/2 beta 3.03 +/- 0.79 and 2.51 +/- 1.10 h; AUC 42.35 +/- 6.20 and 40.60 +/- 6.79mg/L.h. When AUC in tablet was 100%, the relative bioavailability of acetaminophen oral drop was 105.58%. The results showed that the oral drop and tablet are bioequivalent.