Jane Nelson, Republican chairwoman of the Senate Health and Human Services Committee, said everyone who was in line by 11 a.m. would be given a chance to testify, the Austin American-Statesman reported.
Anyone in line after that could fill out a card indicating his or her support or opposition to the bill, she said.
Underground rooms in the Capitol were opened to handle the overflow crowds.
The session has been called solely to hear Senate Bill 1, which would make sweeping changes to the state's abortion regulations.
One local woman opposed to the bill said she was concerned a provision of the bill would shut down abortion clinics, which she said would be "devastating" because they also provided healthcare and family planning to poor women.
Another woman said she and her family had driven from a city 70 miles east of Dallas to register her support for the bill.
"We believe life is sacred," she said.
The first hour of testimony was dedicated to questions from committee members. Four experts, two on each side of the issue, were to testify in the second hour.