He is currently the Spencer T. Olin Professor of Arts and Sciences, and former chair of the Department of Mathematics and Statistics at Washington University in St. Louis.
He works in operator theory and several complex variables, and applications of mathematics to other areas.
[2] He has worked on Toeplitz operators, spaces of holomorphic functions, Nevanlinna–Pick interpolation, extension theorems in several complex variables, and the mathematics of ultrasound and neuroimaging.
In 1995, he, Sheldon Axler and Donald Sarason co-chaired a program at the Mathematical Sciences Research Institute in Holomorphic Spaces.
[3] Jim Agler and he wrote the text Pick Interpolation and Hilbert Function Spaces.