Fibromuscular dysplasia (FMD) is a significant cause of renal artery stenosis, especially in young females. A rare association between FMD and alpha 1-antitrypsin (alpha 1-AT) deficiency has been reported. We compared the alpha 1-AT phenotype distribution in 83 patients with renal arterial FMD with those published for Australian populations. alpha 1-AT phenotyping was performed by isoelectric focusing between pH 4.2 and pH 4.9 on polyacrylamide gels with PiM1M2, PiFM (non-deficiency alleles), PiMS and PiMZ (deficiency alleles) markers. Following phenotyping, alpha 1-AT genotyping was performed in 10 patients to confirm the presence of S and/or Z alleles. The phenotype distribution and allele frequencies were similar to those reported for normal subjects from two Australian populations (72 (86.7%) PiMM phenotype, one (1.2%) PiFM, seven (8.4%) PiMS, two (2.4%) PiMZ and one (1.2%) PiSZ), suggesting that alpha 1-AT deficiency is not a common aetiological factor in renal arterial FMD. However, despite FMD being three times less common in males than females, and carotid artery dissection being a rare occurrence, a male with PiMS deficiency phenotype presented with internal carotid artery dissection and had bilateral renal artery FMD. Further, a patient with PiSZ deficiency phenotype was one of two sisters with FMD and was more severely affected than her PiMM normal phenotype sibling. These two patients from the present series together with nine culled from the literature with alpha 1-AT deficiency phenotype and FMD suggest that the chance combination of alpha 1-AT deficiency and FMD may predispose to severe manifestations of FMD.