Whether it is fair to use personal responsibility of patients for their own health as a rationing criterion in healthcare is a controversial matter. A host of difficulties are associated with the concept of personal responsibility in the field of medicine. These include, in particular, theoretical considerations of justice and such practical issues as multiple causal factors in medicine and freedom of health behaviour. In the article, personal responsibility is evaluated from the perspective of several theories of justice. It is argued that in a healthcare system based on both equality of opportunity and solidarity, responsible health behaviour can—in principle—be justifiably expected. While the practical problems associated with personal responsibility are important, they do not warrant the common knee-jerk refusal to think more deeply about responsibility for health as a means of allocating healthcare resources. In conclusion, the possibility of introducing personal responsibility as a fair rationing criterion is briefly sketched.