About 40 years ago, Thomas McKeown demonstrated that the historic decline in the great killer diseases owed little or nothing to progress in medicine. A generation of research on population health followed, highlighting the large social gradients in health within populations. These vary greatly across societies, but appear largely unrelated to medical care. Medicine was acknowledged as "powerful, but within limits"; the major determinants of health lie elsewhere. We may have missed something. Cuba has achieved "first world" population health status despite a minimal economic base. Far from marginalizing medicine, Cuba has by far the world's largest physician workforce. But doctors' roles are significantly expanded. The system seems to work.