||This study employs the multi-level research methods of archival study and interview to investigate the official exercise of discretion. The focus is the Chinese illegal immigrants seeking to stay on humanitarian grounds. I examined the case files to infer behaviour and attitude of the officials, the Chinese illegal immigrants, and interested parties in the stay assessment process. Apart from the file study, I interviewed the officials, and examined the immigration court cases, intelligence reports, and public documents to get as wide features of the actors and patterns of actions as possible. The empirical part of the thesis utilises the interactional 'two-player' analytical framework developed by the author, arguing that given the often vagueness of policy goals, and unpublished standards for policy enforcement, there are plenty of room for pushes and pulls for both the officials and claimants of programs. The thesis suggests that the stay assessment process was basically a caseload selected by the Chinese illegal immigrants, considering the changes of grounds invoked to claim 'deservingness' to stay to synchronize the political, social, economic, and institutional changes both in Hong Kong and China. Contrary to the commonly held attitude that the Chinese illegal immigrants stand meekly at the official's mercy, they were quite aware of the larger political environments and capable to turn into resources the institutions to promote their interests. The possible prejudice and injustice of denying stay under discretionary power were offset by the biases of discretionary power of granting recognizance pending the process and appeal outcomes, and the discretion to allow departure as and when the Chinese illegal immigrants turned up to withdraw the stay application or the appeal. Multiple contradictions surfaced, at various levels of intensity, throughout the stay assessment process. These contradictions sparked off dynamism for emphasizing and re-emphasizing the discretionary elements of official's decision, and the exceptional features of the claims to stay. The desire for objectivity through legal-rule based control of official discretionary power has shifted the stay process from inquisitorial evidence weighing of 'deservingness' to adversarial legal arguments. The shifts of strategies and responses on both sides of the stay process, it is suggested, heightened tensions and misunderstandings in the community, and changed the focus from soft humanitarian evaluation to cool political and legal assertions. It is also suggested that making the standards public may do more harm on marginal cases, as it increases the burden of persuasion to justify deviation from the published standards.