We describe a family an autosomal dominant myotonic myopathy with absence of the abnormal CTG expansion characteristic of myotonic dystrophy. We believe that the findings in this family concur with those of recent case reports which have postulated the existence of a new adult onset myotonic disorder, distinct from myotonic dystrophy: 'proximal myotonic myopathy'. (C) Harcourt Brace & Co. Ltd 1998.