Pope John Paul, calling himself a sick man among the sick, arrived in the world's premier Roman Catholic "miracle shrine" on Saturday and urged society not to cast aside the old and the suffering.
The 84-year-old Pope, racked by Parkinson's disease and arthritis, began a 32-hour trip to the south-western French city where the Madonna is said to have appeared to the peasant girl Bernadette Soubirous in 1858.
His frailty was evident in his airport arrival address to President Jacques Chirac, which he read slowly, and later at the famous grotto where the visions are said to have taken place.
Aides had rested him on a kneeler to pray but he lost his balance and they had to rush up to prevent him from falling and seated him back on his wheeled throne.
After several minutes of intense prayer, he designated a cardinal to read his address for him, even though it was only four paragraphs long.
"With you I share a time marked by physical suffering, yet not for that reason any less fruitful in God's wondrous plan," he said.
The Pope was then wheeled away for some rest before a planned return to the grotto in the evening for a candlelight procession around the shrine which some 6 million people visit each year, many of them sufferers who pray for miracle cures as they drink holy waters.
But aides say the Pope, who has often urged the sick to find meaning in suffering, has come to pray for others, not himself.
His programme focuses on the traditional Catholic devotion to the mother of Jesus Christ. He will conclude the 104th foreign trip of his pontificate on Sunday with an open-air mass expected to draw at least 300,000 people.
About 150,000 cheering pilgrims lined the route from the airport as church bells pealed. About 2,700 police were on hand, backed up by surveillance helicopters and a battery of anti-aircraft missiles.
The Pope took three sips of the holy water on Saturday.
The Church has recognised 66 cases of what it calls miraculous healings among the thousands of pilgrims who have said they left Lourdes free of their ailments.
In his address to Chirac, the Pope staked a claim for religion's role in modern life, while maintaining full respect for the separation of church and state.
"With respect for the responsibilities and competencies of all, the Catholic Church desires to offer society a specific contribution," he said.
His comments were a challenge to secular France, which this year barred state school pupils from wearing religious insignia and torpedoed Vatican efforts to have the European Union constitution mention the continent's Christian heritage.