The TN work permit is available to Canadians and Mexicans who will engage in an occupation listed under the NAFTA agreement.  That list is available at http://canada.usembassy.gov/visas/doing-business-in-america/professions-covered-by-nafta.html.  When applicable, the TN offers some advantages over the H-1B visa. For example, it is not subject to quotas and it is renewable indefinitely in three-year increments.  In contrast, the H-1B is only available certain times of the year due to quotas and it has a maximum stay of six years. The TN encounters challenges in the green card context as to dual intent and extendibility, but can serve as a good “bridge” or interim visa for a new hire, especially when H-1B quotas have been met.  For example, an employer who identifies a job candidate in December can hire that candidate immediately on a TN work permit and can then file in April to convert the TN to an H-1B.  If the H-1B filing is not selected in April (under the lottery system that is conducted due to the excess demand for H-1B visas), then the employee remains working in TN status for the remainder of the three-year period and can if desired file to convert on the following April for a second chance under the H-1B lottery.  Canadians are visa-exempt and therefore become a TN by simply crossing the border with the correct supporting paperwork from their sponsoring employer.