Renal fibromuscular dysplasia (FMD) can cause hypertension, and previous reports suggest that FMD is familial. We hypothesized that, in families containing an individual with proven FMD, relatives of index cases would have an increased risk of hypertension. ACTA2 mutations cause a spectrum of extra-renal arteriopathy, leading to our second hypothesis that mutations are implicated in FMD. The blood pressure of first-degree relatives was measured using standard devices and, when indicated, with 24-h ambulatory monitoring. Leucocyte DNA was obtained from FMD index cases and ACTA2 sequenced. Thirteen unrelated index cases, aged 2-32 (median 15) years, were recruited. Blood pressure was assessed in 40 first-degree relatives, comprising 22 parents aged 28-58 (median 44) years and 18 siblings aged 3-30 (median 13) years. Hypertension was evident in six (27%) parents but in none of the eight adult siblings. Of the ten screened siblings aged less than 18 years, one teenager was pre-hypertensive (90th-95th centile), the remainder being normotensive. No ACTA2 mutations were found in 13 index cases. Hypertension was evident in 20% of all assessed adult first-degree relatives and is therefore not increased relative to 25% of the adult population. Although hypertensive parents did not undergo angiography to assign FMD status, this observation, together with the lack of hypertension in 18 siblings, indicates that FMD is unlikely to confer an excess hypertension risk in first-degree relatives up to middle-age. Furthermore, in our cohort, FMD was not caused by ACTA2 mutations.