Extending Your Stay
Most non-immigrant visa statuses allow for extensions of time in the United States. The word "extension" in immigration terms means that a student or scholar seeks to continue engaging in the same activity for which he or she originally came to the United States (same school, same lab, same degree program, etc.).
For students the maximum extension time permissible is determined by their school's academic policy on length of degree programs, with the exception of "non-degree" students who have a limit of 2 years in most cases.
For scholars the maximum extension time depends on the visa type. The H-1B visa has a total time of 6 years (with an exception for certain pending permanent residence cases). The J-1 visa in the Research Scholar/Professor category has a limit of 5 years. The J-1 Short-Term Scholar category has a maximum time limit of 6 months.
For more information about extensions and how to request one, check your visa type.