Early intervention services are based on the premise that untreated psychosis may have a deleterious effect on outcome, particularly in the early years of illness. The majority of the studies on duration of untreated psychosis have been conducted in developed countries; therefore this review focuses on publications from developing countries. We also review studies from developing countries that have been published following the Remission in Schizophrenia Working Group criteria. The duration of untreated psychosis is longer in developing countries, and is also associated with poor outcome, whereas remission rates following treatment of first-episode schizophrenia in developing countries appear to be higher than in developed countries. These two findings strongly argue for the establishment of early intervention services for schizophrenia in developing countries.