12- and 24-Month Bars
Once you are in J status, you may be subject to two different rules, the 12- and 24-month bars, which affect how soon you are able to participate in a J-1 Professor or J-1 Research Scholar program.
If you have been in any J status (including J-1 student, J-1 alien physician, J-1 scholar, J-2 dependent, etc.) for more than 6 months and then left the U.S., you are not eligible to return to the U.S. as a J-1 Research Scholar or Professor for 12 months. After the 12 months are over, the bar is lifted and you may return on a J visa for these categories.
If you have completed a J-1 program as a professor or research scholar, you are subject to the 24-month bar once your program is finished. Scholars subject to the bar may not return to the U.S. as a J-1 scholar in the Professor or Research Scholar categories for the 24-month period. This bar also applies to J-2 dependents.