For
Spouses and fiances of US citizens, and their children

Requirements

Fiances
1. Both parties must be legally able to marry.
2. Both must have the intention to marry within 90 days of the fiance coming to the United States.
3. The parties must have personally met within the previous two years (very limited exceptions).

Spouses
1. You must have a pending I-130 petition

Stay
Fiance: 3 months, but can apply for permanent residence after marriage
Spouses: 2 years, during which time you can apply for permanent residence

Notes
Because of long I-130 processing times, it is often faster to bring your spouse and spouse's children to the US on a K visa.

K visa holders are eligible for work permits as soon as they enter the United States.