Fragile X syndrome (FXS) causes learning and emotional problems without mental retardation. Clinical involvement in fragile X is generally believed to result from a lack of fragile X mental retardation 1 (FMR1) protein (FMRP). The physical phenotype of FXS is associated with a connective tissue disorder. Medical complications associated with the connective tissue abnormality in FXS include higher incidence of inguinal or umbilical hernia, gastrooesophageal reflux in infancy, an occasional joint dislocation, particularly at the shoulder, elbow or kneecap, and mitral valve prolapse secondary to a floppy mitral valve, which occurs in approximately 50% of adults with fragile X. The sensitivity that children with FXS demonstrate to visual, tactile, auditory and olfactory stimuli is described collectively as sensory integration dysfunction. The use of psychopharmacology, individual therapy in the language and motor area and psychological interventions can be quite helpful for the developmental and behavioural difficulties associated with FXS.