A fast HPLC method has been developed for simultaneous determination of sultamicillin and its synthesis precursors. The analytes are separated in 2.5 min by means of a Kromasil 100 C18 column (50 mm  2.1 mm i.d., 3.5 mm) at 25 C. The mobile phase (A: 5 mM KH 2 PO 4 and 20 mM KCl adjusted to pH 6.0 with H3PO4 plus 1% THF and B: acetonitrile with 1% THF) was pumped at a flow rate of 0.5 mL min À1 according to the fast gradient mode: 0-0.9 min, 40% B; 0.9-1.0 min, 85% B; 1.0-2.5 min, 85% B; 2.5-2.6 min, 40% B, 2.6-4.0 min, 40% B. Detection was by ultraviolet absorbance at 205 nm. The method was validated in accordance with the International Conference on Harmonisation (ICH) guidelines, good accuracy, intermediate precision ( 3.8%), and linearity being observed for all compounds. This method is sensitive (limits of detection ranged between 0.1-1.1 mg l À1 ) and selective for quantifying sultamicillin and its synthesis precursors and could be used for in-process control.