The present study was designed to assess the safety, tolerability and pharmacokinetics of phenoprolamine hydrochloride floating sustained tablets (PHFST) in healthy Chinese subjects. 116 volunteers were randomized into single- or multiple-dose groups for oral administration 30-240 mg of PHFST once or 60-120 mg twice daily. Safety and tolerability were appraised by monitoring adverse events and laboratory parameters. Pharmacokinetics was assessed by determining the plasma concentrations of phenoprolamine hydrochloride with a validated HPLC method. In single-dose studies, no severe adverse events were observed in volunteers, and all adverse events were mild; the percentages of treatment-emergent events judged to be possibly related to the drug were 3/6 in the 240 mg dose group, 1/6 in the 180-210 mg dose groups, and none in the 30-150 mg dose groups; system exposure (AUC, C(max)) increased with respect to dose at 30-120 mg, whereas AUC raised disproportionately with dose escalating from 120 to 240 mg; the absorption of phenoprolamine hydrochloride was unaffected by food. In multiple studies, no safety concerns were revealed up to 7 days; steady-state plasma concentration was achieved after approximately 4-5 days of repeated twice-daily dosing. PHFST is safe and well tolerated in healthy Chinese subjects. The mean C(max) of PHFST is proportional to dose, but not the AUC. Oral dosing regimen selected for subsequent Phase II/III clinical trials was 60 mg of PHFST, b.i.d., and dose up to 120 mg, b.i.d. - may be used to achieve better antihypertensive effect.