A continuing cause for concern in higher education institutions is the poor core mathematical skills of incoming students. Many institutions now offer mathematics support services such as drop-in centres, online resources and short ‘refresher courses’ in an attempt to alleviate the problem. The majority of third level institutions in Ireland and internationally now make use of diagnostic testing of incoming first year students that both predict subsequent success and select groups for remediation. This project was developed to explore the issues around diagnostic testing and follow-up support for incoming students in the College of Sciences and Health. A large cohort of first year science students was tested and those who failed to achieve 50% on the test were offered support. This support came in the form of peer-assisted student led tutorials during which students had the opportunity to revise basic areas of mathematics. On comparison of the scores on the diagnostic test with the end of module results we have noticed a correlation between students who scored poorly on the diagnostic test and students who failed the Semester 1 mathematics module. The key recommendations arising from this study are; diagnostic testing provides useful information about the cohort as a whole and provides lecturers with information about gaps in the prior knowledge of the group allowing them to take particular care when introducing new topics, diagnostic testing helps to identify those students who are significantly weaker than the rest of the cohort and thus enables them to be targeted with support and attention. Furthermore, by carrying out diagnostic testing over an extended period of time, trends can be observed. This information can then be used by Schools or Departments in an attempt to cope with diversity and ensuring that follow-up support is adequately provided.