Surgical ablation of the cardiac neural crest from the chicken embryo results in persistent truncus arteriosus (PTA) and a change in the elastic laminae of the great vessels, wherein elastin and the elastin microfibril show significant spatial disorder. The purpose of this study was to test the hypothesis that the interstitial collagens would also be disordered in the elastic laminae of chicken embryos with PTA. The birefringence characteristics of interstitial collagen were examined to evaluate spatial ordering. The results showed that collagen in the elastic laminae assumed an orderly configuration of well-defined fiber bundles in the great vessel walls of control embryos, whereas vessels from embryos with PTA lacked any distinct spatial order. Collagens type I and III were localized in the vessel walls. Type III collagen was the principal collagen of the elastic laminae, but was absent from the intima of all vessels. In the elastic laminae of vessels from control embryos, collagen type III showed well-defined fiber bundles whereas embryos with PTA had diffuse collagen type III in poorly defined laminae that were not separated by discrete layers of smooth muscle cells. Collagen type I was a minor component of the elastic laminae but formed robust pericellular fiber bundles throughout the media and intima. Collagen type I fibers appeared to be coarsened and less uniform in the vessels from embryos with PTA.