The objectives of this work were to develop a method to measure the tensile properties of individual cotton fibers and to use the data from the method to study the relationships between the tensile properties of individual fibers and fiber bundles. Mathematical models were developed to predict bundle strength from individual fiber tensile prop erties. The single fiber strength method gives information about the elongation and crimp of cotton fibers. For the set of samples used in this work, the average elongation was 11.8% and the average crimp was 4.8%. Analysis of the single fiber strength data suggests that the average single fiber breaking strength sets an upper limit for the fiber bundle strength. The correlations between fiber strength and yam strength were some what improved by using the average single fiber strength rather than the Stelometer or high volume instrument ( HVI ) bundle strength.