A binary gradient HPLC assay was developed for the separation and quantitation of carbamazepine (CBZ),carbamazepine-epoxide (CBZ-ep), carbamazepine-10,11-trans-diol (CBZ-diol), carbamazepine-2-hydroxide (CBZ-OH),carbamazepine-3-hydroxide (CBZ-3OH) and carbamazepine-acridan (CBZ-acr) extracted from patient urine. The internal standard was 10-methoxy-carbamazepine. The initial phase was 70:15:15 phosphate buffer-methanol-acetonitrile followed by a linear gradient commencing at 13 minutes to 50:35:15 phosphate buffer-methanol-acetonitrile at 24 minutes. The flow rate was constant at 2 mL/min. The UV absorbance detector wavelength was changed at 18 minutes from 240 nm to 280 nm. Typical retention times for CBZ-diol, CBZ-2OH, CBZ-ep, CBZ-3OH, CBZ-acr, CBZ and internal standard were 5.26, 8.36, 10.46,12.51,14.2, 23 and 27.53 minutes respectively. The minimum quantifiable limit (MQL) for all of the analytes was 0.2 μg/mL except for CBZ-2OH where the MQL was 2 μg/mL. Precision and accuracy of the assay was 1.3 to 19.4% for the 6 analytes.