Ehlers-Danlos Syndrome is a rare hereditary connective tissue disorder produced by collagen abnormalities. The Type IV variant causes vascular rupture in the second and third decades. Definitive diagnosis at present is based on demonstrating a deficiency of Type III collagen or procollagen chemically or in fibroblast cultures. Both require fresh tissue. We have shown in fixed autopsy tissue that the elastin in two EDS IV patients appears accordion-pleated with a high waviness index (WI) of 1.58 +/- 0.028 (n = 90) compared to 1.35 +/- 0.08 (n = 446) for 21 controls aged 9 to 71. The WI is the ratio of the length of elastin in the internal elastic lamina to the circumference. The group were significantly different statistically (p less than 0.01) with a randomized block design analysis. Vessel size and age did not alter the WI in either controls or patients. There was significant overlap of data points between the two groups so that no conclusions can be drawn on individual vessels. However, if the waviness index is greater than 1.8, the vessels are unlikely to be normal. We did not study patients with other connective tissue diseases. The WI may be a useful qualitative guide of abnormality in a retrospective study if the diagnosis of Ehlers-Danlos Type IV is entertained.