Hypermobility, using Beighton's mobility score, was present in 9.5% of 377 ballet dancers. Females were more mobile than males. A direct relationship was found between forward flexion and both the duration of dance training and age. This suggests that forward flexion is acquired, and unlike generalized hypermobility, which was found among family members of the hypermobile group. None of the hypermobile dancers studied had evidence of mitral valve prolapse but injuries were significantly more common compared to controls (p less than 0.05). We regard hypermobility as a liability to the ballet dancer.