A simple high performance liquid chromatographic procedure was described for the determination of amoxicillin, ampicillin, cloxacillin, dicloxacillin, flucloxacillin and phenoxymethylpenicillin (penicillin V) in single or combined pharmaceutical formulations. The drugs were chromatographed on an Ultrasphere ODS column and (40% methanol containing 9 mM-sodium heptane sulphonate, 30 mM-potassium dihydrogen phosphate and 0.04% triethylamine) adjusted to pH 5 with 1 M-phosphoric acid as mobile phase using penicillin G as internal standard. The flow rate was 1 ml.min.-1 at 230 nm detection. The results show good accuracy as shown by the % recovery of 99.61, 99.53, 99.9, 100,08, 100.18 and 99.908 and high precision as shown by the relative standard deviation, RSD 0.744, 0.613, 0.557, 0.731, 0.46 and 0.308