The Instrument for Analysis of Science Teaching (IAST) was developed as a 26-category system of interaction analysis. Following conceptualization and several research studies, the IAST was redeveloped with 14 basic categories (IAST Base) and an expanded 32-categories version (LAST v.2) which is based on subdividing the IAST Base categories. In this paper the IAST Base and the IAST v.2 are described and some ideas for using the system with preservice and inservice teachers and supervisors are given for research studies and teacher feedback. (Author/AL)