[1] He taught at the University of Munich, from 1973 to 1975 and again in 1978,[citation needed] where Professor Joseph Ratzinger, the future Pope Benedict XVI, was teaching as an associate.

[citation needed] Wielgus was appointed Bishop of Płock on 24 May 1999 by Pope John Paul II,[2] and was consecrated by Cardinal Józef Glemp on 1 August of that year.

[citation needed] As he concluded his service in Płock, he was made an honorary citizen of the city in recognition of "his work to develop knowledge, culture, and Christian beliefs".

[17] On 20 December 2006, journalists found documents from the dictatorship's archives according to which Archbishop Wielgus collaborated—or at least conversed—with the secret police during communist rule in Poland.

[18][failed verification] The process of review of the Security Service's files, known in Poland as lustration (Pol: Lustracja) has been the source of many political scandals in recent years.

The Polish human rights ombudsman, Janusz Kochanowski, said on 4 January 2007 that there was evidence in the secret police archives that Archbishop Wielgus knowingly cooperated with the dictatorship.

[citation needed] Archbishop Wielgus acknowledged that he signed a cooperation statement in 1978, but insisted that he did so only under coercion and disputed the length and characterization of his contact as described in the published reports.

[citation needed] The day after the discovery of the incriminating documents on 20 December 2006, the Vatican Press Office announced that "The Holy See, in deciding the nomination of the new archbishop of Warsaw, took into consideration all the circumstances of his life, including those regarding his past" and said that Pope Benedict "has full trust in his excellency Msgr.