This publication brings together five chapters from Disease Control Priorities in Developing Countries, 2nd edition (2006), along with an introduction and a conclusion by WHO. The chapters cover mental disorders, neurological disorders, learning and developmental disabilities, and alcohol and illicit opiate abuse. The purpose of this special package is to provide information on cost-effectiveness of interventions for these specific groups of disorders. This information should contribute to reformulation of policies and programmes and reallocation of resources, eventually leading to reduction o.