In this study, we conducted a survey of all tertiary level institutions in Ireland to find out how many of them use diagnostic tests, and what kind of mathematical content areas and topics appear on these tests. The information gathered provides an insight into what instructors expect students to know on entry to university and what they expect students to have difficulty with. In total, 12 diagnostic tests from 11 Irish institutions were collected during the study. An item-by-item analysis was carried out on each diagnostic test to determine the content areas and topics that are assessed on the diagnostic tests and to identify any additional knowledge required for successful completion. We compare the tests administered in the university sector and the Institute of Technology (IT) sector of the Irish tertiary level education system. In addition, current diagnostic tests are compared with two tests from the 1980s to see if the level of mathematical preparedness expected of first-year students has changed over time. Our analysis is situated in a discussion of previous research on diagnostic testing both nationally and internationally.