He worked at the Institute of Mathematics of the Polish Academy of Sciences since 1960. In the years 1986-2002 he was the Director of the Institute. He was an outstanding mathematician, the creator of a strong school working on partial differential equations. He is in particular well-known for the Ahlfors-Bers-Bojarski Theorem concerning the solutions of the Beltrami equation. He combined his scientific work with organizational activities. In the years 1970-1981 he was the director of the Institute of Mathematics of the University of Warsaw. He created the Research and Conference Center in Będlewo. For his service to the Polish science he was awarded the Golden Cross of Merit, the Knight's Cross of the Order of Polonia Restituta and the Commander's Cross with the Star of the Order of Polonia Restituta.