We investigate whether the cap rate, that is, the rent-price ratio in commercial real estate incorporates information about future expected real estate returns and future growth in rents. Relying on transactions data spanning several years across fifty-three metropolitan areas in the U.S., we find that the cap rate captures fluctuations in expected returns for apartments, retail, as well as industrial properties. For offices, by contrast, the cap rate does not forecast returns even though adsditional evidence reveals that expected returns on offices are also time-varying. We link this varying success of the cap rate in forecastings commercial property returns to differences in the stochastic properties of their rental growth rates. The growth in office rents has a higher correlation with expected returns and is more volatile than for other property types. Taken together, these characteristics diminish the correlation between the cap rate and the future returns to offices.