The 2012 IEEE 5th International Conference on Cloud Computing (CLOUD 2012) is co-located with the 8th IEEE 2012 World Congress on Services (SERVICES 2012), the 2012 IEEE 19th International Conference on Web Services (ICWS 2012), the 2012 IEEE 9th International Conference on Services Computing (SCC 2012), the 2012 IEEE 1st International Conference on Mobile Services (MS 2012), and the IEEE 2012 1st International Conference on Services Economics (SE 2012). It was formally promoted by the IEEE Computer Society in 2003, and is now the most prestigious professional conference dedicated to cloud computing. The CLOUD 2012 Research Track accepted 48 papers out of 282 paper submissions with an acceptance rate of 17%. The other technical program tracks include the Applications & Experiences Track, the Industry Track, and the Work-in-Progress Track. The technical program covers a broad scope of the state-of-the-art research and development efforts in cloud computing. All accepted papers are published by the IEEE Computer Society Press in the CD-ROM and online versions of the Proceedings of CLOUD 2012.