This study has been carried out as a part of the IRIS, which is a collaborative research project, supported by the European Commission (7th Framework program). It intends to identify the factors involved in the choice of STEM subjects by the university students of the Punjab. Seven major factors have been discussed which play a role in the choice and retention of students in STEM areas in higher education. These factors include impact of school experience, personal choice of students, importance of subject area, experience as student in the subject, expectations of everyday life, educational status of students in the subject and priorities for future. This study also digs out the gender mean difference in the choice of subject. A structured questionnaire IRIS-Q was used containing items regarding the influence of various factors for the choice of STEM subjects. Only those students were the part of study that had completed their first year of education in any area of STEM in the public sector universities of Punjab. Results indicated that school experience was identified as an important factor for the selection of STEM subjects. Among the family and relatives the role of fathers was prominent in the choice of STEM areas. The role of media and technology had no significant role to motivate the students to choose the subjects. Students' learning endeavours played an effective role for the retention of students in STEM areas. Future priorities like job security had been identified as major factors for retaining in STEM subjects. The study explored that there was significant gender difference among the perception of respondents in their self-efficacy, personal satisfaction and future opportunities. It was recommended that the attention of all other stakeholders should be drawn to foster STEM education in Pakistan.