ABC News announces Charles Gibson will become sole anchor of "World News Tonight."
Gibson will continue as co-anchor of "Good Morning America" until June 30.
Following the death of anchorman Peter Jennings last August, Elizabeth Vargas and Bob Woodruff were named co-anchors of the broadcast.
Woodruff has since been recovering from serious injuries he received while reporting in Iraq.
The network says Vargas has chosen to step down to take maternity leave.
She'll return to co-anchor "20/20" and ABC News specials.
Gibson will begin his solo position on May 29.