TWO mathematicians, a Frenchman and a Russian working in the United States, were presented yesterday with the Fields Medal, an international honor equal in mathematics to the Nobel Prize.

　　President Jiang Zemin joined in handing out the medals during the annual International Congress of Mathematics, which is being held at the Great Hall of the People, the seat of the Chinese legislature in central Beijing.

　　Laurent Lafforgue was honored for work on number theory and the "Langlands program,'' a group of theories about links between groups of numbers and equations.

　　Lafforgue, 35, is a professor at the Institute of Advanced Scientific Studies in Bures-sur-Yvette, France.

　　Vladimir Voevodsky was recognized for developing new theories in topology, or the science of shapes.

　　Voevodsky, 36, is a professor at the Institute for Advanced Study in Princeton, New Jersey. He also has taught at Harvard and Northwestern universities.

　　The medal is given every four years by the International Mathematical Union to a mathematician under age 40.

　　It is named for the late Canadian mathematician John Charles Fields, organizer of the 1924 International Mathematics Congress. It was first awarded in 1936.

　　Some 4,120 people are attending the congress, the biggest gathering of mathematicians in the world. It runs through Aug. 28.

　　Also yesterday, Madhu Sudan of the Massachusetts Institute of Technology was awarded the Nevanlinna Prize in theoretical computer science.

　　Sudan, born in Chennai, India, was recognized for work on proving mathematical statements by computer and for error-correcting codes used in compact disc recordings and the Internet.