If Texas, Oklahoma, Oklahoma State or Texas Tech decide to leave the Big 12, joining the Pac-12 won't be an option.
Twelve is enough for the Pac-12, putting the Big 12 in position to survive yet again.
The Pac-12 presidents and chancellors voted late Tuesday night not to expand again. Commissioner Larry Scott says "after careful review we have determined that it is in the best interests of our member institutions, student-athletes and fans to remain a 12-team conference."
Texas, Oklahoma, Oklahoma State and Texas Tech were among those considering a potential move from the Big 12. After expanding from the Pac-10 with new members Utah and Colorado last year, members of the new Pac-12 won't give them the chance.
Meanwhile, across the county in New York, Big East Commissioner John Marinatto said his members "pledged to each other that they are committed to move forward together."
The Big East also has been staring at an uncertain future after Pittsburgh and Syracuse announced last weekend they are moving to the Atlantic Coast Conference.
But now it appears the Big East, like the Big 12, stands a good chance to survive the latest round of conference realignment in college athletics.
On Monday, the board of regents at Texas and Oklahoma voted to give their presidents the right to choose a new conference. Oklahoma State's regents have scheduled a special meeting Wednesday about conference realignment.
University of Oklahoma President David Boren has said the two in-state rivals will remain in the same league whether they decide to stay in the Big 12 or join the Pac-12.
"Whatever we do, we're going to do it together, and I think that's very good news for the state of Oklahoma," Boren said.
Texas Tech was going to follow Texas' lead.
Texas and Oklahoma were not acting together. Texas officials had stated several times it wanted to keep the Big 12 alive.
Oklahoma officials said they were looking for stability and equal revenue sharing, which does not occur in the Big 12. Texas has its own cable television network.
A person familiar with the schools' discussions said Texas and Oklahoma officials are expected to meet in the next few days to negotiate an agreement to keep the universities in the league for at least the next five years. The person requested anonymity because the meeting had not been announced.
Whether other schools would be invited to join that meeting was unclear Tuesday night.