This study was to investigate the synergistic taste effect between monosodium glutamate (MSG) and 5`-ribonucleotides consisted of disodium 5`-inosinate (IMP) and 5`-guanylate (GMP) as 1 : 1 ratio. Solvent was distilled water. Sensory evaluation with 10 panelists was performed by using ratio scaling method (magnitude estimation). The results were as follows; 1) Taste intensities were increased, as nucleotides content to MSG increased. 2) Multiple regression analyses were carried out with the taste intensity data as a function of nucleotides content at three concentrations of seasonings, 0.025%, 0.05% and 0.1%. 3) Predicted taste intensities(Y_P) were calculated from the regression equation. Also taste intensity ratios(Y_(TR))-Y_(TR)=Y_P/taste intensity of MSG only-were calculated. 4) The taste intensity ratios(Y_(TR)) at three concentrations of seasonings in the same nucleotides contents showed about the same. Therefore, instead of above regression equations, only one multiple regression equation expressing Y_P of nucleotides seasonings could be determined, as functions of nucleotides content and seasoning concentration.