Myotonia and muscle weakness are cardinal features of myotonic disorders including the myotonic dystrophies and the non-dystrophic myotonias. Despite the recent progress in molecular genetics of these myotonic disorders, the precise mechanisms responsible for myotonia and for permanent or episodic muscle weakness are still unclear. Treatment has been mostly symptomatic, independent of the disease process involved. Moreover, there have been few randomized controlled trials of treatment for myotonic disorders and consequently no standardized treatment regimens are available. We present a review of selected treatment trials in the myotonic disorders and in muscle channelopathies, and discuss, on the basis of our experience in the myotonic disorders, the limits and advantages of treatment trials in this field. Future genotype-phenotype correlations using the patch-clamp technique are also illustrated.