As Pope, Paul continued the reforms of John XXIII.
He reconvened the Second Vatican Council, and supervised implementations of many of its reforms, such as the vernacularization and reform of the liturgy.
He instituted an international synod of bishops; bishops were instructed to set up councils of priests in their own dioceses.
Powers of dispensation devolved from the Roman Curia onto the bishops, rules on fasting and abstinence were relaxed, and some restrictions on intermarriage were lifted. A commission to revise canon law revision was established.
In 1964, Paul made a pilgrimage to the Holy Land and became the first pope in over 150 years to leave Italy.
That was followed by trips to India in 1964, the United States in 1965, where he addressed the United Nations, Africa in 1969, and Southeast Asia in 1970.
Relations between the Vatican and the Communists improved, and Communist leaders visited the Vatican for the first time.
Paul met with leaders of other churches, and in 1969 addressed the World Council of Churches, and limited doctrinal agreements were reached with the Anglicans and Lutherans.
Paul issued frequent reassertions of papal primacy in the face of growing dissent within the Roman Catholic Church itself.
He enlarged the college of cardinals, and added cardinals from third world countries.
In the 1968 encyclical Humanae Vitae, Paul reaffirmed the church's ban on contraception, a disappointment to many liberals.
It led to protests, and many national hierarchies openly modified the statement.
Liberals raised questions about priestly celibacy, divorce, and the role of women in the church, but Paul held to traditional church positions.