Gene therapy is set to revolutionise medicine. The ability to replace the function of a missing or faulty gene offers millions of people with life-threatening, rare conditions, the potential for longer, healthier lives. In some cases, a single one-time treatment can provide a lifetime of benefits. But gene therapies are expensive and this raises important questions about how we should value and pay for them. These therapies provide huge benefits for patients, for their families and for broader society. But how can this value be assessed over entire lifetimes and compared to the value of conventional medicines that often have to be taken for life? We also need an infrastructure that quickly identifies those who can benefit from gene therapy and then delivers it in a timely fashion. How must our healthcare systems evolve? This New Scientist debate brings together leading thinkers in healthcare to explore these questions as we prepare for this new era of medicine.