Title in English: “Studies in student teachers’ language use in teaching situations”. Subtitle: “Experiments in analyzing stereotypic expressions by three different measures”. When student teachers by videotape technology have been confronted with their own teaching at two teaching sessions to assess their language use, it has been shown that they have done very well in their estimation of themselves. As the “objective” measure educational experts were used. The differences in perception between student teachers and educational experts were greatest at the categories of stereotypic expressions, incomplete sentences and grammatically incorrect expressions. Of these, stereotyped expressions were selected out of the material to be examined closer linguistically. After a measure of the degree of stereotypy had been constructed, the student teachers were ranked by their greater or lesser use of stereotypical expressions of high or moderate values. This measure is considered realistic and when experts and student teachers were compared against this standard it was revealed that the student teachers underestimated their performance closer to a realistic value than the educational experts had done. When the change in the positive or negative direction from the first to the second lesson was compared, the result was the same. The student teachers had noticed some stereotypic expressions and succeeded in changing the prevalence of them in a positive direction, that is, a decrease took place. During an inspection of the expressions that were perceived, it could be seen that they mostly coincided with the expression with high stereotype value. These belong mainly to the category of unusual clause modifying adverbs, such words and expressions that can be interpreted as signs of hesitancy in the performance or as too modern phenomena to be suitable in teaching. Those who did not have the same tendency to be observed were mainly shorter query expressions and confirmation of student responses in the classroom. Finally, it has been noted that you have to judge the results in light of the particular speech situation where the expressions of question and answer often require formalization, while freer text can be said to require greater variation in the teacher’s language use. Stereotypical expressions as disturbance factor thus appear mostly where the teachers are unfettered by the textbook and express themselves in longer series of speech.