The ITIL 2011 Editions have been updated for clarity, consistency, correctness and completeness. ITIL is based upon a lifecycle approach and the core guidance consists of five publications:

• ITIL Service Strategy
• ITIL Service Design
• ITIL Service Transition
• ITIL Service Operation
• ITIL Continual Service Improvement.

Each of the five publications represents a stage in the ITIL service lifecycle. With each stage influencing and relying upon the others, the lifecycle moves cyclically from service strategy (where the business requirements are set) to the design, transition, operation and continual improvement of IT services.