The historical relationship between price-earnings ratios and subsequent stockmarket performance is examined, and why history might not repeat itself this time is discussed. Strong historical evidence is found that high price-earnings ratios have been followed by disappointing stockmarket performance in the short and long-term. Specifically, high price-earnings ratios have been followed by slow long run growth in stock prices. Moreover, when high price-earnings ratios have reduced the earnings yield on stocks relative to returns on other investments, short-run stockmarket performance has suffered as well. Despite this evidence, it is concluded that we cannot rule out the possibility that these historical relationships are of little relevance today due to fundamental changes in the economy.