The pontiff, abandoning his prepared sermon, compared the wild excesses of the ancient Roman empire to 21st century society and urged people to rediscover their faith.
"In our times we need to say 'no' to the largely dominant culture of death," Benedict said during his improvised homily in the frescoed Sistine Chapel where he was elected pope last April.
"(There is) an anti-culture demonstrated by the flight to drugs, by the flight from reality, by illusions, by false happiness ... displayed in sexuality which has become pure pleasure devoid of responsibility," he added.
Benedict did not spell out what he meant by a "culture of death", but the phrase was a rallying cry of his predecessor John Paul who regularly used the term to define abortion and artificial birth control.