This paper sums up partial results of a long-term project aimed at determining specific needs in teaching advanced English students at the Institute of Foreign Languages of the Faculty of Education, Palacký University, where both authors have been teaching for more than 15 years. In our advanced English students, we have long observed a tendency to make quantitative mistakes, that is to use certain English language structures with a remarkably different frequency than the frequency typical for texts composed by English native speakers. Through a series of quantitative analyses of our students' texts in comparison with authentic English texts, we have been trying to identify the areas of major quantitative discrepancies, which, in turn, helps us make our teaching to advanced students more focussed and effective. The present contribution maps the theoretical background of the functions and usage of various forms of the English infinitive, and comments on the frequency of usage of various forms and syntactic positions of the infinitive in authentic English texts and in texts produced by our 3rd year Bachelor students in the written part of their final English language examination. [For the complete volume, "Rethinking Directions in Language Learning and Teaching at University Level," see ED594626.]