Abstract: Kalman filtering spectrophotometry was investigated to assay the contents of vitamin B₁, vitamin B₆, chlordiazepoxide, dihydralazine sulfate, promethazine hydrochloride and hydrochlorothiazide in compound reserpine tablets consisting of 10 components. Absorption proportionality constant for each component was obtained by the application of non-negative least square method. The average recoveries for each were 97～103% with CV% ≤6.9 except vitamin B₁ (n=11).