The advances in sequencing technologies and the availability of molecular testing for a rapidly increasing number of diseases are both promising and challenging. Here, we will focus on practical aspects and the usefulness of molecular diagnosis in a clinical setting. Even in the absence of therapeutic consequences, genetic testing can and should be considered for a number of reasons, including a right to know for the patient and the family, and the avoidance of further diagnostic work-up. As it will soon become possible to routinely sequence hundreds or even thousands of genes in parallel, molecular diagnosis will become increasingly important as it provides valuable information for the physician and for the affected individuals.