What is it? How might it be taught? Can we measure it? These questions will be considered within a range of contexts from calculus-based courses for scientists and engineers to completely hands-on courses for prospective grade K-8 teachers. I will introduce a relatively easy to use problem solving assessment instrument we have developed, as well as other methods of probing problem solving skills in our introductory students. Results of measurements made at a variety of institutions, and in a variety of courses, will be presented, and I share my view of the implications for improving instruction.