Student Number : 0316775W - MSc research report - Faculty of Science / This qualitative research project investigated the ideas of a small group of learners in the first year physics course at the University of the Witwatersrand in the area of atmospheric (air) pressure. These ideas constitute the prior knowledge with which these learners enter physics education at tertiary level. Clinical interviews were conducted with an initial sample of three (3) respondents, and the main study consisted of seven (7) first-year physics students. Data obtained during the course of the interviews was audio-taped and transcribed, and from an analysis of the transcripts a picture was obtained of the content of the knowledge held, and of the epistemological and ontological views that respondents entertained. What renders this work important is the argument that teachers are unable to assist the learning process without engaging actively with what their learners already know and believe. The first step in setting up learning experiences which can assist learners to become fluent in the construction of sound scientific explanations for phenomena and to become competent at weighing evidence is to determine the state of learners’ prior knowledge. The findings of this limited case study may be summed up as follows: There is very little indication, in the sample investigated in this study, that any meaningful learning has occurred in the areas of pressure, atmospheric pressure and the kinetic theory. These concepts have little or no explanatory power for learners in attempting to account for natural phenomena and technological applications in which atmospheric pressure is at work.