At the 1984 Los Angeles Games, Gross became the first East German to earn a gold medal in swimming when he won the 100 meter freestyle. He also took gold in the 100 meter butterfly.
Four years later in Seoul, Gross won gold in yet another event, the 200 meter butterfly.
After a brief retirement, Gross came back to swim for a unified Germany at the 1991 World Championships in Perth, Australia.
He finished second in the 200 meter butterfly and swam on the winning 4x200 meter relay team which upset a heavily-favored U.S. squad.