Selective preventive measures, which target particular subgroups of the population who may be more susceptible to a disorder, but who are still symptom free, offer a way of overcoming the prevention paradox. However, selective intervention is not without its challenges because it relies on an efficient means of identifying those at increased risk (via single-stage or multistage screening). Apart from the increased risk of psychosis in those with a positive family history, our ability to identify these at-risk individuals prior to the onset of schizophrenia is currently poor and will therefore need to await future research efforts, discussed later in this article and in the other articles in the volume. The sensitivity and specificity of the screens must also be balanced with the safety and efficacy of any proposed intervention.