These temporary visas allow an alien to enter the United States for a specified period of time and for a specific purpose. Below are some of the classes of nonimmigrant worker visas:

H-1B Visa:

A visa for an occupation defined as a specialty occupation. Some examples of specialty occupations are engineering, accounting, finance, medicine, and law. To qualify, the applicant must have a bachelor's degree or higher and a license if required.  Duration of stay in the US is generally six years. To apply for an H-1B visa, the applicant must be sponsored by a U.S. employer. A change of jobs requires submitting a new application.

E Visa:

The E Visa applies only to aliens originating in countries with which the US has a treaty. E-1 visas are limited to those who seek entry for the purposes of carrying on substantial trade, while E-2 visas are limited to those who have invested or are in the process of making an investment in a business here. Duration of stay is two years, but qualifying individuals can elect to extend their status indefinitely.

O Visa:

This is available to highly talented or acclaimed individuals, such as artists, athletes, entertainers, scientists, and business people. No limit exists on the duration of stay; authorization to stay depends on the activity that brings the alien to the US.

P Visa:

Performing entertainers and athletes may qualify for the P visa. P-3 visas are more appropriate for group of artists who will be in the United States for a specific period of time and fall under the category of "culturally unique" artists.  Duration of stay includes the time needed to complete the activity. Extensions of up to a year may be granted.

R-1 Visa:

The R visa is open to religious workers who wish to enter the United States to continue their vocation within a religious denomination that has a bona fide, nonprofit organization here. Period of stay can't exceed five years, but an extension of two years can be granted.

TN Visa:

This visa applies only to Canadian and Mexican nationals employed in one of 63 professions listed under the North American Free Trade Agreement (NAFTA). Duration of stay can't exceed one year, and one-year extensions can be granted.