Small fast folding subdomains with low contact order have been postulated to facilitate the folding of larger proteins. We have tested this idea by determining how the fastest folding linear beta-hairpin, CLNO25, which folds on the nanosecond time scale, folds within the context of a two-hairpin WW domain system, which folds on the microsecond time scale. The folding of the wild type FBP28 WW domain was compared to constructs in which each of the loops was replaced by CLNO25. A combination of FTIR spectroscopy and laser-induced temperature-jump coupled with infrared spectroscopy was used to probe changes in the peptide backbone. The relaxation dynamics of the beta-sheets and beta-turn were measured independently by probing the corresponding bands assigned in the amide I region. The folding rate of the CLNO25 beta-hairpin is unchanged within the larger protein. Insertion of the beta-hairpin into the second loop results in an overall stabilization of the WW domain and a relaxation lifetime five times faster than the parent WW domain. In both mutants, folding is initiated in the turns and the beta-sheets form last. These results demonstrate that fast folding subdomains can be used to speed the folding of more complex proteins, and that the folding dynamics of the subdomain is unchanged within the context of the larger protein.