The objective of this study is to statistically evaluate tensile mechanical properties of two kinds of carbon/polyimide composites, i.e., Celion 6K/PMR-15 and T800H/PMR-15 with a quasi-isotropic stacking sequence. Tensile tests were conducted under room temperature using about thirty smooth specimens each. Mechanical properties measured are ultimate strength, failure strain, elastic modulus, and Poisson's ratio. Statistical analyses use four kinds of distribution models such as normal, log-normal, type-I extreme-value, and two-parameter Weibull distributions. These analyses derive the estimates of central tendencies and scatter parameters, and B allowables. Moreover, the modified Kolmogorov-Smirnov goodness-of-fit test for the four kinds of distribution models is applied for the data of each mechanical property. Correlation between mutual mechanical properties is examined, and a multiple regression analysis applied to predict the ultimate strength.