Buprenorphine is a partial mu agonist and kappa antagonist which is used for the treatment of pain and opioid addiction. A mixture of buprenorphine hydrochloride and naloxone hydrochloride has been approved for the treatment of opioid dependence. In this study a third order derivative spectrophotometric method based on zero-crossing technique has been used for the simultaneous determination of buprenorphine hydrochloride and naloxone hydrochloride in tablets. The measurements were carried out at wavelengths of 257.8 (zero-crossing point of naloxone hydrochloride) and 252.2 nm (zero-crossing point of buprenorphice hydrochloride) for buprenorphine hydrochloride and naloxone hydrochloride, respectively in the third order derivative spectra obtained in methanol and 0.1 M NaOH (50: 50) as solvent. The method was found to be linear in the range of 20-80 mu g/mL for buprenorphine hydrochloride and 5-20 mu g/mL for naloxone hydrochloride. The within-day and between-day coefficient of variation and error values were less than 2.5% and 1.8%, respectively. The proposed method was successfully used for simultaneous determination of these drugs in pharmaceutical dosage form without any interference from excipients or need to prior separation before analysis.