Triple-helical peptides (THPs) have been utilized as collagen models since the 1960s. The original focus for THP-based research was to unravel the structural determinants of collagen. In the last two decades, virtually all aspects of collagen structural biochemistry have been explored with THP models. More specifically, secondary amino acid analogs have been incorporated into THPs to more fully understand the forces that stabilize triple-helical structure. Heterotrimeric THPs have been utilized to better appreciate the contributions of chain sequence diversity on collagen function. The role of collagen as a cell signaling protein has been dissected using THPs that represent ligands for specific receptors. The mechanisms of collagenolysis have been investigated using THP substrates and inhibitors. Finally, THPs have been developed for biomaterial applications. These aspects of THP-based research are overviewed herein.