A study was conducted to evaluate reliability of the longitudinal tensile properties of unidirectional CFRP laminates. Four kinds of CFRP were tested in order to examine the factors of variability and have the information concerning reliability improvement. Temperature dependence of the strength and its variability were investigated by means of testing at three kinds of temperatures. Statistical distributions of the respective mechanical properties were obtained from the tensile tests with large sample size. As a result, toughening the matrix resin was proved to increase the strength and improve the reliability of CFRP.