In spite of the abundance of publications describing university faculty development programs and activities, little is known about the effectiveness of such programs on specific disciplines or subject areas. The fact that differences have been identified in the dimensions on which students of different university departments rate their teachers suggests that instructors of different departments need different types of programs for teaching improvement. This article describes a study that has looked into methods for improving instruction of university physics full professors with many years of teaching experience. Two methods for this aim were examined for effectiveness: a workshop and individualized consultation, both augmenting students' midterm ratings of their instructors. Analysis of pre- and postworkshop questionnaires reveals impressive improvement on the majority of items, particularly those of specific teaching techniques discussed in the workshop, but not on the global ratings of the teacher. The special consultation procedure has been shown to bring about substantial increase on overall teaching performance. We conclude that veteran teachers are often unable to improve significantly their overall teaching performance when provided with midterm feedback from students' questionnaires or when participating in a workshop for teaching improvement. Improving their instruction requires substantial and continuous expert consultation as well as investing substantial time and efforts of their own.