The aim of this study was to examine how Microsoft PowerPoint is used by science teachers in Trinidad and Tobago and to gauge from teachers what considerations influence their decision to use PowerPoint presentations in their science teaching. A total of 20 secondary school science teachers were observed using PowerPoint in the delivery of science lessons. The findings indicate that science teachers used PowerPoint slides largely as glorified lectures to present information to students. Some teachers used PowerPoint to introduce their lessons and some to summarise lessons. A few teachers used it interactively throughout their science lessons to engage students in various teaching and learning activities. Two teachers observed did not use PowerPoint themselves, but instead encouraged their students to use it to present findings of research assignments. Interviews following the observations revealed that even though teachers have recognized the effectiveness of PowerPoint as a teaching and learning tool, they are not always deliberate in their decision about the specific ways in which they decide to use PowerPoint.