cDNA encoding the C-terminal domain (nt2283 to 3714) of type III collagen was amplified by PCR in five overlapping products and examined for mutations in 13 patients with Ehlers-Danlos syndrome type IV (EDS IV) with uncharacterised lesions and in five control patients with known single base mutations. Six different point mutations were detected by denaturing gradient gel electrophoresis (DGGE), in addition to those in the known controls. Four of seven patients who had no point mutations in this region were shown to lack complete exons from their amplified cDNA. Mutations were detected in all patients with typical or acrogeric EDS IV, but only in one of four individuals with the atypical form of the disease.