Pope Caps Africa Trip with Big Mass in Benin

* Big, colourful crowd at last main event on trip

* Papal document appealed for honest leadership

* Pope holding up well despite heat and humidity

By Philip Pullella

COTONOU, Benin, Nov 20 (Reuters) - Pope Benedict celebrated a big open-air Mass on Sunday, capping a trip to Africa where he appealed to leaders to serve their people honestly and to developed nations to shun a condescending, know-it-all attitude towards the continent.

The crowd of some 50,000 people in Cotonou's Friendship Stadium in the largest city of Benin went wild as the pope entered. His reception in the West African country has been by far one of the most exuberant on all of his 22 foreign trips.

The crowd, many dressed in colourful robes and dresses emblazoned with his picture, danced and swayed as they chanted in the local Fon language and French.

In his homily in French, the pope urged his listeners "to be attentive to the cry of the poor, the weak and the outcast" and sent a special greeting "those affected by AIDS or other illnesses, to all those forgotten by society".

The 84-year-old German pope has held up well on the three-day trip despite the heat and high humidity. Vatican spokesman Father Federico Lombardi said the pontiff's health was fine.

While Sunday's closing event was a ceremony of worship, the main purpose of the trip, the pope's second to Africa since his election in 2005, was to sign a major papal document he wrote to address the Roman Catholic Church's view of the continent's future.

In the document, which reflected the results of a synod of African bishops at the Vatican in 2009 and was signed on Saturday, he told African leaders that justice was a fundamental prerequisite of peace and prosperity.

It also said African leaders must shun corruption and use natural resources for the good of their people and that Catholics in Africa should have good ties with Islam and traditional religions without compromising their own identity.

In its brief section on AIDS, the pope avoided directly addressing the issue of the use of condoms to fight the spread of the disease.

He sparked controversy in 2009 when he told reporters on his plane to Africa that condoms could actually spread Aids. The Vatican later said his remarks were taken out of context.

In the document, known as an Apostolic Exhortation, the pope said AIDS was, above all, an ethical problem.

He called for a "change of behaviour" and repeated the Church's teaching that the best way to fights AIDS is sexual abstinence, rejection of sexual promiscuity, and fidelity within marriage.

During the trip he also said the developed world should not look down on Africa "with the judgmental tone of a moraliser" and impose rules, but had to come up with real solutions of partnership to help solve the continent's many problems.

The pope said he chose Benin as the sole venue to deliver his document because in many ways the former French colony was exemplary. Benin made one of Africa's few peaceful transitions to democracy in 1990 after a period of Marxist-Leninist rule that had been supported by the former Soviet Union and Cuba.

Unlike some of its neighbours where inter-religious strife is rife, particularly Nigeria, Benin enjoys mostly peaceful coexistence between Christianity, Islam and traditional religions. (Reporting By Philip Pullella)