Abstract(#br)Following a government campaign run by the Independent Commission Against Corruption (ICAC) in 1994, many Hong Kong companies and trade associations adopted written codes of conduct. The research study reported here examines how and why companies responded, and assesses the impact of code adoption on the moral climate of code adopters. The research involved (a) initial questionnaire surveys to which 184 organisations replied, (b) longitudinal questionnaire-based assessments of moral ethos and conduct in a focal sample of 17 code adopting companies, (c) interviews with 33 managers in the focal companies examining the adoption and impact of the codes, and (d) content analysis of 41 company codes of conduct, including those of most focal companies, plus the ICAC model... code.(#br)While a mixture of prudential and altruistic reasons were given for code adoption, content analysis suggested that the prime motive was corporate self-defence. The prevailing themes were bribery, conflict of interest, insider information, gambling, moonlighting, accuracy of records and misuse of corporate assets. Wider social responsibility tended to be neglected. Companies appeared to have imposed their codes top-down, emphasising disciplinary procedures rather than ethics training, and appointing neither ethics counsellors nor ombuds-people. The longitudinal study over a seven month period suggested that while moral ethos may have declined, overall standards of perceived conduct had not changed.