Three patients with Ehlers-Danlos syndrome type IV (EDS IV) and biochemical evidence of structural defects in collagen III were investigated for mutations within the collagen III gene (COL3A1). Single strand conformation polymorphism analysis of alpha 1 (III) cDNA indicated the presence of different heterozygous sequence changes in each of the patients. Nucleotide sequencing revealed mutations leading to the substitution of glycine 400 with glutamic acid, glycine 595 with cysteine, and glycine 1003 with aspartic acid. EDS IV is a life-threatening disorder which, as the clinical histories of our patients and their families show, still often escapes diagnosis. Biochemical and molecular studies can clarify the diagnosis and help provide appropriate management and counselling.