The intention of this study was to determine how science instructors in the university laboratories spend time on instruction. The study, was guided by three research questions and two hypotheses tested at 0.05 level of significance. The study employed a non-participant observation case study design. 48 instructors teaching lower and higher levels practical courses in Botany, Microbiology, Zoology, Chemistry, Physics, and Geology in Faculty of Science of Delta State University constituted the sample. A behaviour checklist called Science Laboratory Interaction Categories (SLIC) was the instrument used for data collection. A major finding of the study showed that science instructors spend most of the instructional time on; Demonstration of Procedure, Shows, Transmits, Listens and Non-lesson related behaviours resulting in less investigative teaching. Another finding of the study shows that among the six science disciplines the data revealed significant differences for all the instructor behaviours. It was concluded that the observation of what science instructors do in the university laboratories can be a source of valid information on how to improve science education in the universities and science teachers training for other levels of education and institutions.