In recent years the literature on Catholic school leadership in Australia and elsewhere has grown considerably. Comparatively little has been written from the persepective of practitioners. In general, the findings of this research study suggest that lay principals of Catholic secondary schools understand the role of principal of a diocesan secondary school as a ministry within the Catholic Church. While the informants did not use overtly theological terms to articulate this understanding, the accounts of their experience in principalship and the insights gained through reflection on their leadership behaviour have led them to believe that they are in fact exercising a legitimate ministry within the field of Catholic secondary education in Victoria. This research has brought to light a body of knowledge about the work of a group of principals which has not previously been subject to critical scrutiny. While the study is of intrinsic merit in recognising and describing the work of secondary lay principals, from an instrumental perspective these findings raise a number of issues relating to the preparation, induction and support available to newly appointed and continuing principals in diocesan Catholic secondary schools in Victoria. The study is situated in the specific setting of Catholic secondary schools in the State of Victoria but it may offer insights to practitioners and/or system authorities in faith-based schools of whatever denomination.