Wait time, the duration of teacher pauses after questions, is an important variable in research on science teaching. This project investigated the effects of increasing teacher's wait times on general questioning skills in science teaching. In previous research, the influence of wait time training has been confounded with instruction in general questioning skills, making it difficult to test the hypothesis that increasing the wait time will by itself improve classroom discussions. In this project, these variables were separated through the use of four treatment groups made up of science teachers. One group received instruction in wait time using a newly developed electronic feedback device that monitors the duration of teacher and student pauses; a second group received instruction in general questioning skills; a third group received both types of instruction; a comparison group received no instruction of either type. The tape recordings were coded and analyzed for classroom interaction data. Comparisons were made using discriminant analysis, analyses of variance, and correlational relationships. The wait time feedback devices facilitated the production of wait time means consistently superior to baseline performance, albeit slightly below the 3-second criterion sought. Regardless, the feedback groups did produce a large number of the hypothesized changes. Significant effects were found from a comparison of the discriminant function scores. Effects consistently favored the groups with the feedback devices. The presence of the guides seemed to make little difference. The groups with the devices used greater numbers of high-level questions, especially those of the evaluative level. There were more contributions from students, as measured by length of answers, frequency of volunteered contributions, numbers of relevant student words, and percentages of student talk.