We investigate long-term cointegrative and short-term causal relations among seven U.S. sectoral REITs. First, cointegration tests identify one long-term cointegrative relation among five of the sectors, which suggests that two of the sectors are outside the cointegrative space. Second, short-term Granger causality tests identify three leading and two following cointegrated sectors. Third, a proposed vector autoregressive model indicates that a stronger cointegrating effect is induced by declining real estate markets and a multivariate sensitivity regression model shows that unexpected inflation significantly and negatively influences the cointegrative disequilibrium. Lastly, our cointegration-based portfolio performance analyses show that the inferior performance of the all-sector market portfolio stems from containing the redundant cointegrated sectors which shatter portfolio diversification.