In the winter term of 1979-1980, 692 faculty members and 1,319 students responded to a library use study conducted at the Technishe Universitat Wien (Vienna, Austria). Among other topics, the hours of operation of the main library were studied. Results show that more than 50% of the faculty and more than 70% of the students consider the circulation desk's hours of operation insufficient. The reading room and photocopy department's hours were only moderately criticized. Other results indicate: it is not necessary to open the library on Saturdays; the majority of respondents accept the summer closing period (3 weeks in August); and frequent and intensive library users consider the library's hours of operation more restrictive than do occasional or infrequent users. Graphs and tables showing survey results are included. (Author/THC)