Objective: The present study aims to analyze the male-students’ premarital sex and to identify the drivers and challenges of observing chastity. Method: This applied research was conducted through a qualitative approach and with a phenomenological method. The statistical population was the male-students of Ferdowsi University in Mashhad, and 48 undergraduates of them were interviewed in a semi-structured way with a purposeful sampling method "with maximum diversity" and analyzed using the three-step coding method of Strauss and Corbin. Results: The expressions expressed by the participants were classified into 858 concepts, 62 categories, and 14 themes. Examining the lived experiences of the students, the findings of study, with some negligence, were divided into three parts: the reasons why they enter into an illegitimate relationship, the reasons why they leave an illegitimate relationship, and the reasons why they avoid an illegitimate relationship. The themes inferred in the first part include the religion of permissiveness, the decline of indigenous identity, the domination of sexual desires, psychological issues, the stimulating social media context, self-deception, and the unattainable dream of marriage, and the themes of the second part include orienting to spirituality, being zealous, and thinking about the consequences. The harmfulness of an illegitimate relationship, satisfaction of sexual desires through other ways, the lack of conditions for an illegitimate relationship, and the choice of chastity include the four themes of the third part. . Conclusion: The most important challenges of observing chastity, and the factors of entering into an illegitimate relationship (i.e. the barriers of chastity) are: ‘the sexual desire’, ‘the impossibility of its legitimate satisfaction, ‘the permissible and highbrow spirit’ and ‘the social and media stimulating atmosphere’; the main drivers of chastity in the this statistical population were faith, ‘still awake’ moral conscience, religious-moral family atmosphere, and social control.