Characteristics of H-1B Specialty Occupation Workers: Fiscal Year 2016 Annual Report to Congress, October 1, 2015 - September 30, 2016 [open pdf - 3MB]
"The H-1B nonimmigrant classification is a vehicle through which employers may obtain workers on a temporary basis. The program is designed to provide employers the opportunity to employ qualified workers who are not otherwise authorized to work in the United States. Employers may file an H-1B petition for an alien to perform services in a specialty occupation, services of an exceptional nature relating to a Department of Defense (DOD) cooperative research and development project or coproduction project, or services of distinguished merit and ability in the field of fashion modeling. [...] Although USCIS [U.S. Citizenship and Immigration Services] is responsible for evaluating an alien's qualifications for the H-1B classification and effecting a change of nonimmigrant status for aliens already in the United States in another nonimmigrant classification, approval of an H-1B petition does not guarantee issuance of an H-1B visa or admission to the United States in H-1B status."
U.S. Citizenship and Immigration Services: http://www.uscis.gov/