Certain conditions and activities may make an applicant ineligible for a visa. Examples of these ineligibilities include: drug trafficking; overstaying a previous visa; and submitting fraudulent documents. If you are ineligible for a visa, you will be informed by the consular officer and advised whether there is a waiver of the ineligibility available to you and what the waiver process is. Classes of Aliens Ineligible to Receive Visas contains the complete list of ineligibilities.