As is known the new Turkish Commercial Code (TCC) brought up many innovations regarding the corporate law. The liability of the executive board members is based on a differentiated solidarity instead of absolute solidarity and the duty of care is based on business judgment rule instead of prudent man rule. Despite the fact that this new concept is not prescribed in the article 369/1 of the Turkish Commercial Code, we can see it in the rationale of the provision itself. In this study the prudent man and the business judgment rules are reviewed as well as the reasons behind this transformation.Keywords: Prudent man rule, business judgment rule, liability of the board of managers