The Japanese stock market is noted for its high valuation level compar
ed to other advanced stock markets. Previous work attributes this valu
ation disparity to institutional factors. This paper examines the fund
amental determinants of the relative valuation of Japanese and US stoc
ks within a simple comparative valuation model. It estimates the impac
t of fundamental economic variables on relative stock price indices. A
mong the notable findings is the role of exchange rates, retained earn
ings, and the effect of regulatory changes as determinants of relative
stock valuation between the two countries. The cost of capital is see
n to exert only a minor influence.