No, a visa does not guarantee entry into the United States. The visa allows you to travel to a U.S. port-of-entry (airport, for example) and request permission of the Department of Homeland Security immigration inspector to enter the U.S. Generally, however, if you have been honest during your visa interview regarding your past visits and the purpose of your current visit, the immigration inspector will approve your request for permission to enter the U.S. by placing an entry stamp in your passport. The immigration inspector will also decide how long you can stay in the U.S. for any particular visit.