A new method for simultaneous determination of metronidazolum and vitamin B6 was established by the third derivative spectrophotometry in 0.1 mol/L HCl solution. The detection limits were 0.81 microg/mL for metronidazolum and 0.16 microg/mL for vitamin B6. The linear range of determination was 1.6-22.4 microg/mL for both metronidazolum and vitamin B6. This method has been applied to the determination of metronidazolum and vitamin B6 in tabellae metronidazoli compositae with satisfactory results. The coefficients of variation are below 2.26 and 2.65% and the recoveries are 93-102% and 99-101% for metronidazolum and vitamin 6, respectively.