Mutations in the gene encoding fibrillin 1 (FBN1) cause Marfan syndrome (MFS), and related connective tissue disorders. The disease spectrum is wide and while many genotype–phenotype correlations have been reported, few have been consistent. In this study FBN1 was analyzed in 113 patients with MFS or Marfan-like features. Fifty-three mutations were identified in 52 individuals, 41 of which were novel. The mutations comprised 26 missense, 11 splice site, 7 frameshift, 6 nonsense, 1 in-frame deletion, and 2 whole exon deletions. In common with previous studies, genotype–phenotype analysis showed that a FBN1 mutation was more likely to be identified in patients fulfilling Ghent criteria (P = 0.005) and in those who had ectopia lentis (EL) (P < 0.0001). Other previously reported genotype–phenotype correlations were also considered and a new inverse association between a mutation in exons 59–65, and EL emerged (P = 0.002). © 2009 Wiley-Liss, Inc.