The effects of fiber slack on bundle tensile properties are investigated through computer simulation. The results have shown that the amount of fiber crimps in a bundle affects the bundle breaking elongation without altering the bundle breaking strength, while the standard deviation of fiber crimps in a bundle affects the bundle breaking strength but not the bundle breaking elongation. The L(e)/e curve of a bundle can be used as an indicator of the existence of fiber slack in a bundle. The results from the computer simulation have been compared with that from HVI tensile tests.